UNIT CARBON AND ITS COMPOUNDS 11

Learning Objectives

After studying this lesson, the student will be able to: ‹ know the importance of organic compounds. ‹ classify the organic compounds and name them based on IUPAC rules. ‹ identify the functional groups of organic compounds. ‹ explain the preparation, properties and uses of ethanol and ethanoic acids. ‹ know the composition and preparation of soap and detergent. ‹ understand the cleansing action of soap and detergents. ‹ differentiate soap and detergents.

INTRODUCTION are called organic compounds. In this lesson, you will learn about carbon compounds. You have studied, in your lower classes, that carbon is an inseparable element in human 11.1 GENERAL life as we use innumerable number of carbon CHARACTERISTICS OF ORGANIC COMPOUNDS compounds in our day to day life. Because, the food we eat, medicines we take when ill, clothes Everything in this world has unique we wear; domestic and automobile fuels, paint, character, similarly organic compounds are cosmetics, automobile parts, etc., that we use unique in their characteristics. Some of them contain carbon compounds. The number are given below: of carbon compounds found in nature and man-made, is much higher than that of any � Organic compounds have a high molecular other element in the periodic table. Infact weight and a complex structure. there are more than 5 million compounds of � They are mostly insoluble in water, but carbon. The unique nature of carbon, such soluble in organic solvents such as ether, as catenation, tetravalency and multiple carbon tetrachloride, toluene, etc. bonding, enables it to combine with itself � They are highly inflammable in nature or other elements like hydrogen, oxygen, � Organic compounds are less reactive nitrogen,sulphur etc., and hence form large compared to inorganic compounds. Hence, number of compounds. All these compounds the reactions involving organic compounds are made of covalent bonds. These compounds proceed at slower rates. 155

10th_Science_Unit-11.indd 155 21-02-2019 18:40:56 � Mostly organic compounds form covalent atoms are linked in a linear pattern to form bonds in nature. the chain. If all the carbon atoms in the chain � They have lower melting point and boiling are connected by single bonds, the compound point when compared to inorganic is called as saturated. If one or more double compounds bonds or triple bonds exist between the � They exhibit the phenomenon of isomerism, carbon atoms, then the compound is said to in which a single molecular formula unsaturated. represents several organic compounds that differ in their physical and chemical CH3-CH2-CH3 CH3-CH=CH2 properties Propane Propene � They are volatile in nature. Saturated compound Unsaturated compound � Organic compounds can be prepared in the 2. Cyclic Compounds: Organic laboratory compounds in which the chain of carbon atoms is closed or cyclic are called cyclic 11.2 CLASSIFICATION OF compounds. If the chain contains only carbon ORGANIC COMPOUNDS atoms, such compounds are called carbocyclic BASED ON THE PATTERN compounds. If the chain contains carbon and OF CARBON CHAIN other atoms like oxygen, nitrogen, sulphur, etc., these compounds are called heterocyclic What is the significance of classification? compounds. Carbocyclic compounds are There are millions of organic compounds further subdivided into alicyclic and aromatic compounds. Alicyclic compounds contain known and many new organic compounds one or more carbocyclic rings which may be are discovered every year in nature or saturated or unsaturated whereas aromatic synthesized in laboratory. This may mystify compounds contain one or more benzene organic chemistry to a large extent. However, rings (ring containing alternate double bonds a unique molecular structure can be assigned between carbon atoms). E.g. to each compound and it can be listed by

using systematic methods of classification Carbo cyclic compounds and eventually named on the basis of its H H C CH C structural arrangements. In early days, 2 2 HC CH or or chemists recognised that compounds having HC CH H2C CH2 HC CH Benzene similar structural features have identical H2C CyclCHobutane 2 HC AromCHatic Compound chemical properties. So they began to classify Alicyclic Comporound or HC CH H2C CH2 C compounds based on the common structural HC CH H Cyclobutane Benzene or Aromatic Compound arrangements found among them. Alicyclic CoHCmpHetrocyclicound CH compounds O o HC CH Organic chemistry is the chemistry of Furan Heterocyclicor Compound catenated carbon compounds. The carbon HC CH O o atoms present in organic compounds are Furan linked with each other through covalent bonds Heterocyclic Compound and thus exist as chains. By this way, organic compounds are classified into two types as Figure 11.1 depicts the classification of follows: organic compounds based on the pattern of 1. Acyclic or Open chain compounds: carbon arrangements and their bonding in These are the compounds in which the carbon organic compounds:

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10th_Science_Unit-11.indd 156 21-02-2019 18:40:56 Organic compounds

Acyclic or Open chain Cyclic or Closed chain compounds compounds

Saturated Unsaturated Heterocyclic (Compounds Carbocyclic (double or triple Compounds (Ring containing C-C Compounds bond) containing carbon and bonds) (Only cabon Ethene CH = CH other element) E.g.Ethane ring) Ethyne CH = CH E.g Pyridine, Furan C H

Alicyclic Aromatic Compounds Compounds E.g Cyclobutane E.g Benzene

Figure 11.1 Classification of organic compounds

11.3 CLASSES OF ORGANIC (b) Alkenes: The hydrocarbons, which contain COMPOUNDS (BASED ON one or more C=C bonds are called alkenes. THE KIND OF ATOMS) These are unsaturated compounds. They are represented by the general formula CnH2n. The Other than carbon, organic compounds simplest alkene contains two carbon atoms contain atoms like hydrogen, oxygen, nitrogen, (n=2) and is called ethylene (C2H4). etc., bonded to the carbon. Combination of these (c) Alkynes: The hydrocarbons containing carbon kinds of atoms with carbon gives different classes to carbon triple bond are called alkynes. They of organic compounds. In the following section, let are also unsaturated as they contain triple us discuss various classes of organic compounds. bond between carbon atoms. They have the

general formula CnH2n – 2. Acetylene (C2H2) 11.3.1 Hydrocarbons is the simplest alkyne, which contains two The organic compounds that are composed carbon atoms. Table 11.1 lists the first five of only carbon and hydrogen atoms are called hydrocarbons of each class: hydrocarbons. The carbon atoms join together Table 11.1 Hydrocarbons containing 1to 5 to form the framework of the compounds. These carbon atoms are regarded as the parent organic compounds No. of and all other compounds are considered to be carbon Alkane Alkene Alkyne derived from hydrocarbons by replacing one atoms (CnH2n + 2) (CnH2n) (CnH2n - 2) or more hydrogen atoms with other atoms or Methane - - 1 group of atoms. Hydrocarbons are, further, sub (CH4) divided into three classes such as: Ethane Ethene Ethyne 2 (C2H6) (C2H4) (C2H2) (a) Alkanes: These are hydrocarbons, which Propane Propene Propyne 3 contain only single bonds. They are represented (C3H8) (C3H6) (C3H4) by the general formula CnH2n + 2 (where n = Butane Butene Butyne 4 1,2, 3, ……). The simplest alkane (for n=1) is (C4H10) (C4H8) (C4H6) methane (CH4). Since, all are single bonds in Pentane Pentene Pentyne 5 alkanes, they are saturated compounds. (C5H12) (C5H10) (C5H8)

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10th_Science_Unit-11.indd 157 21-02-2019 18:40:57 11.3.2 Characteristics of 11.3.3 Classification of organic hydrocarbons: compounds based on functional groups � Lower hydrocarbons are gases at room temperature E.g. methane, ethane are gases. The structural frameworks of organic compounds are made of carbon and hydrogen, � They are colourless and odourless. which are relatively less reactive. But, the � The boiling point of hydrocarbons increases presence of some other atoms or group of with an increase in the number of carbon atoms makes the compounds more reactive and thus determines the chemical properties atoms. of the compound. These groups are called � They undergo combustion reaction with functional groups.

oxygen to form CO2 and water. � Alkanes are least reactive when compared A functional group is an atom or group to other classes of hydrocarbons. of atoms in a molecule, which gives its characteristic chemical properties. � Alkynes are the most reactive due to the The chemical properties of an organic presence of the triple bond. compound depend on its functional group � Alkanes are saturated whereas alkenes and whereas its physical properties rely on remaining part of the structure. Carbon to alkynes are unsaturated. carbon multiple bonds (C=C, C C) also are � They are insoluble in water. considered as functional groups as many of the properties are influenced by these bonds. Other Test to identify saturated and unsaturated functional groups include atoms of halogens, compounds: –OH, –CHO, –COOH, etc. � Take the given sample solution in a test For example, ethane is a hydrocarbon tube. having molecular formula C2H6. If one of its hydrogen is replaced by –OH group, you will � Add a few drops of bromine water and get an alcohol. Leaving the functional group, observe any characteristic change in colour. the rest of the structure is represented by ‘R’. � If the given compound is unsaturated, it Thus an alcohol is represented by ‘R-OH’ will decolourise bromine water. � Functional Saturated compounds do not decolourise Group bromine. CH3-CH3 CH3-CH2-OH Ethane Ethanol Hydrocarbon Alcohol

ALKANE ALKENE Does not react with Will react with bromine A series of compounds containing the bromine water, and water, and as such also does not decolourise decolourises same functional group is called a class of bromine water bromine water organic compounds. Table 11.2 shows various classes or families of organic compounds and their functional groups: ADDITION OF BROMINE WATER TO ALKANES AND ALKENES

Figure 11.2 Test to identify unsaturated compounds

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10th_Science_Unit-11.indd 158 21-02-2019 18:40:57 Table 11.2 Classes of organic compounds based on functional group

Class of the Functional Common Formula Examples compound group

Alcohols –OH R-OH Ethanol, CH3CH2OH

O || Aldehydes R-CHO Acetaldehyde, CH3­CHO −C−H

O || Ketones R–CO-R Acetone, CH3COCH3 −C−

O || Carboxylic acids R-COOH Acetic acid, CH3COOH −C−OH

O Methyl acetate, Ester || R-COOR −C−OR CH3COOCH3 R-O-R Ether –O–R Dimethyl ether, CH3OCH3

11.4 HOMOLOGOUS SERIES 11.4.1 Characteristics of homologous series Homologous series is a group or a class of organic compounds having same general � Each member of the series differs from the formula and similar chemical properties in preceding or succeeding member by one which the successive members differ by a - methylene group (–CH2) and hence by a CH2 group. molecular mass of 14 amu. Let us consider members of alkanes given � All members of a homologous series in Table 11.1. Their condensed structural contain the same elements and functional formulas are given below: group. � They are represented by a general molecular Methane - CH4

formula. e.g. Alkanes, CnH2n + 2. Ethane - CH3CH3 � The members in each homologous series Propane - CH3CH2CH3 show a regular gradation in their physical Butane - CH3(CH2)2CH3 properties with respect to their increase in Pentane - CH3(CH2)3CH3 molecular mass. If you observe the above series. you can � Chemical properties of the members of a notice that each successive member has one homologous series are similar. methylene group more than the precedent � All the members can be prepared by a member of the series and hence they are called common method. homologs.

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10th_Science_Unit-11.indd 159 21-02-2019 18:40:57 11.5 NOMENCLATURE OF Table 11.3 Root words of hydrocarbons ORGANIC COMPOUNDS No. of carbon atoms Root word 1 Meth- 11.5.1 Why do we need 2 Eth- nomenclature? 3 Prop- In ancient days, the names of organic 4 But- compounds were related to the natural things 5 Pent- from which they were obtained. For example, the formic acid was initially obtained by 6 Hex- distillation of ‘red ants’. Latin name of the red 7 Hept- ant is ‘Formica’. So, the name of the formic acid 8 Oct- was derived from the Latin name of its source 9 Non- Later, the organic compounds were synthesized 10 Dec- from sources other than the natural sources. So scientists framed a systematic method for (ii) Prefix: The prefix represents the naming the organic compounds based on their substituents or branch present in the parent structures. Hence, a set of rules was formulated chain. Atoms or group of atoms, other than by IUPAC (International Union of Pure and hydrogen, attached to carbon of the parent chain Applied Chemistry) for the nomenclature of are called substituents. Table 11.4 presents the chemical compounds. major substituents of organic compounds and 11.5.2 Components of an IUPAC respective prefix used for them: name Table 11.4 Prefix for IUPAC Name

The IUPAC name of the any organic Substituent Prefix used compound consists of three parts: -F Fluoro i. Root word -Cl Chloro ii. Prefix iii. Suffix -Br Bromo These parts are combined as per the -I Iodo

following sequence to get the IUPAC name of -NH2 Amino the compound: -CH3 Methyl

Prefix Root Word Suffix IUPAC Name -CH2CH3 Ethyl

(i) Root word: It is the basic unit, which (iii) Suffix describes the carbon skeleton. It gives the The suffix forms the end of the name. It number of carbon atoms present in the parent is divided into two parts such as (a) Primary chain of the compound and the pattern of their suffix and (b) Secondary suffix.The primary arrangement. Based on the number of carbon suffix comes after the root word. It represents atoms present in the carbon skeleton, most of the nature in carbon to carbon bonding of the names are derived from Greek numerals the parent chain. If all the bonds between the (except the first four). Table 11.3 shows the root carbon atoms of the parent chain are single, then words for the parent chain of hydrocarbons suffix ‘ane’ has to be used. Suffix ‘ene’ and ‘yne’ containing 1to10 carbon atoms: are used for the compounds containing double

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10th_Science_Unit-11.indd 160 21-02-2019 18:40:57 and triple bonds respectively. The secondary specify its location and identity. suffix describes the functional group of the compound. 11.5.4 IUPAC Nomenclature of hydrocarbons – Solved Table 11.5 Suffix for IUPAC Name examples Class of the Functional Let us try to name, systematically, some Suffix used Compound group of the linear and substituted hydrocarbons by following IUPAC rules: Alcohols −OH -ol Example 1: CH3-CH2-CH2-CH2-CH3 Aldehydes −CHO -al Step 1: It is a five- carbon chain and hence the root word is ‘Pent’. (Rule 1) O Ketones || -one Step 2: All the bonds between carbon atoms are −C− single bonds, and thus the suffix is ‘ane’. Carboxylic So, its name is Pent + ane = Pentane −COOH -oic acid acids Example 2:

11.5.3 IUPAC rules for naming CH3 | organic compounds: CH3−CH−CH2−CH2−CH3 � Rule1: Identify the longest chain of carbon Step 1: The longest chain contains five atoms to get the parent name (root word). carbon atoms and hence the root word is ‘Pent’. � Rule 2: Number the carbon atoms of the Step 2: There is a substituent. So, the carbon parent chain, beginning at the closest chain is numbered from the left end, which is end of the substituent or functional closest to the substituent. (Rule 2)

group. These are calledlocant numbers. CH3 1 |2 3 4 5 If both functional group and substituent are CH3−CH−CH2−CH2−CH3 present, then the priority will be given to the functional group. Step 2: All are single bonds between the � Rule 3: In case of alkenes and alkynes, carbon atoms and thus the suffix is ‘ane’. locate the double bond or triple bond and Step 3: The substituent is a methyl group use its locant number followed by a dash and it is located at second carbon atom. So, its and a primary suffix. The carbon chain is locant number is 2. Thus the prefix is ‘2-Methyl’. (Rule 6). numbered in such a way that the multiple The name of the compound is bonds have the lowest possible locant 2-Methyl + pent +ane = 2-Methylpentane number. � Rule 4: If the compound contains functional Example 3: group, locate it and use its locant number CH3 followed by a dash and a secondary suffix.

CH−− � Rule 5: When the primary and secondary 2 CH − CH− CH − CH − CH − CH suffixes are joined, the terminal ‘e’ of the 3 2 2 2 3 primary suffix is removed. Step 1: The longest chain contains seven � Rule 6: Identify the substituent and use a carbon atoms and hence the root word is ‘Hept’. number followed by a dash and a prefix to Step 2: There is a substituent. So, the

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10th_Science_Unit-11.indd 161 21-02-2019 18:40:57 carbon chain is numbered from the end, which Step1: The parent chain consists of 3 is closest to substituent. (Rule 2) carbon atoms. The root word is ‘Prop’. 1 CH3 Step 2: There are single bonds between the carbon atoms of the chain. So, the primary 2 −− CH2 suffix i s ‘a n e’. CH − CH− CH − CH − CH − CH 3 3 4 2 5 2 6 2 7 3 Correct Step 3: Since, the compound contains – OH group, it is an alcohol. The carbon chain is

CH3 numbered from the end which is closest to –OH group. (Rule 3) CH−−2

CH3− CH− CH2− CH2− CH2 − CH3 3 2 1 1 2 3 4 5 6 CH − CH − CH − OH Wrong 3 2 2

Step 4: The locant number of –OH group is Step 2: All are single bonds between the 1 and thus the secondary suffix is ‘1-ol’. carbon atoms and thus the suffix is ‘ane’. The name of the compound is Step 3: The substituent is a methyl group Prop + ane + (1-ol) = Propan-1-ol and it is located at third carbon. So, its locant number is 3. Thus the prefix is ‘3-Methyl’. Note: Terminal ‘e’ of ‘ane’ is removed as per (Rule 6) Rule 5 Hence the name of the compound is Example 2: CH COOH 3-Methyl + hept + ane = 3 –Methylheptane 3 Step1: The parent chain consists of 2 Example 4: CH3-CH2-CH2-CH=CH2 carbon atoms. The root word is ‘Eth’. Step 1: It is a ‘five- carbon atoms chain’ and Step 2: All are single bonds between the hence the root word is ‘Pent’. (Rule 1) carbon atoms of the chain. So the primary Step 2: There is a carbon to carbon double suffix is ‘ane’. bond. The suffix is ‘ene’. Step 3: Since the compound contains Step 3: The carbon chain is numbered from the–COOH group, it is a carboxylic acid. The the end such that double bond has the lowest secondary suffix is ‘oic acid’ locant number as shown below: (Rule 3): The name of the compound is 5 4 3 2 1 Eth + ane + oic acid) = Ethanoic acid CH3− CH2− CH2− CH= CH2 Table 11.6 lists IUPAC names homologs of Step 4: The locant number of the double various classes of organic compounds bond is 1 and thus the suffix is ‘-1-ene’. Test yourself: So, the name of the compound is Pent + (-1-ene) = Pent-1-ene Obtain the IUPAC name of the following compounds systematically:

11.5.5 IUPAC Nomenclature of (a) CH3CHO other classes – Solved (b) CH CH COCH examples 3 3 3 (c) ClCH2-CH2-CH2­-CH3 Example 1: CH3-CH2-CH2-OH

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10th_Science_Unit-11.indd 162 21-02-2019 18:40:57 Table 11.6 IUPAC Name of various classes of compounds

No. of IUPAC Name carbons atoms Alcohols Aldehydes Ketones Carboxylic acid Methanol Methanal Methanoic acid 1 - (CH3OH) (HCHO) (HCOOH) Ethanol Ethanal Ethanoic acid 2 - (CH3CH2OH) (CH3CHO) (CH3COOH) Propanol Propanal Propanone Propanoic acid 3 (CH3CH2CH2OH) (CH3CH2CHO) (CH3COCH3) (CH3CH2COOH) Butanol Butanal Butanone Butanoic acid 4 (CH3CH2CH2CH2OH) (CH3CH2CH2CHO) (CH3COCH2CH3) (CH3CH2CH2COOH)

5 Pentanol Pentanal Pentanone Pentanoic acid (CH3CH2CH2CH2 CH2OH) (CH3CH2CH2CH2 CHO) (CH3COCH2CH2 CH3) (CH3CH2CH2CH2 COOH)

11.6 ETHANOL (CH3CH2OH) (ii) Addition of Nitrogen source Molasses usually contains enough nitrogenous Ethanol is commonly known as alcohol. matter to act as food for yeast during the All alcoholic beverages and some cough syrups fermentation process. If the nitrogen content contain ethanol. Its molecular formula is of the molasses is poor, it may be fortified C H OH. Its structural formula is 2 5 by the addition of ammonium sulphate or Ethanol

H H ammonium phosphate.

H C C O H (iii) Addition of Yeast C H OH H H 2 5 The solution obtained in step (ii) is collected in large ‘fermentation tanks’ and yeast is added to it. The mixture is kept at about 303K for a few 11.6.1 Manufacture of ethanol days. During this period, the enzymes invertase and zymase present in yeast, bring about the Ethanol is manufactured in industries conversion of sucrose into ethanol. by the fermentation of molasses, which is a

by-product obtained during the manufacture invertase C H O + C H O C12H22O11 + H2O C6H12O6 + C6H12O6 12 22 11 2 glucose6 12 6 6fructose12 6 of sugar from sugarcane. Molasses is a Sugar glucose fructose dark coloured syrupy liquid left after the zymase crystallization of sugar from the concentrated C6H12O6 2C2H5OH + 2 CO2 glucose6 or12 fructose6 ethanol2 5 2 sugarcane juice. Molasses contain about 30% glucose or fructose ethanol of sucrose, which cannot be separated by The fermented liquid is technically called crystallization. It is converted into ethanol by wash. the following steps: (iv) Distillation of 'Wash' (i) Dilution of molasses The fermented liquid (i.e. wash), containing Molasses is first diluted with water to bring 15 to 18 percent alcohol, is now subjected to down the concentration of sugar to about 8 to fractional distillation. The main fraction drawn 10 percent. is an aqueous solution of ethanol which contains

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10th_Science_Unit-11.indd 163 21-02-2019 18:40:58 95.5% of ethanol and 4.5% of water. This is called (iii) Oxidation: rectified spirit. This mixture is then refluxed Ethanol is oxidized to ethanoic acid with over quicklime for about 5 to 6 hours and then alkaline KMnO4 or acidified 2K Cr2O7 allowed to stand for 12 hours. On distillation of

this mixture, pure alcohol (100%) is obtained. + K2Cr2O7 / H This is calledabsolute alcohol. CH3CH2OH CH3COOH +H2O 2[O] Ethanoic acid More to know During this reaction, the orange colour Yeast and Fermentation: Yeasts are of K2Cr2O7 changes to green. Therefore, this reaction can be used for the identification of single–celled microorganisms, belonging alcohols. to the class of fungi. The enzymes present in yeasts catalyse many complex organic (iv) Esterification: reactions. Fermentation is conversion of The reaction of an alcohol with a carboxylic complex organic molecules into simpler acid gives a compound having fruity odour. This molecules by the action of enzymes. E.g. compound is called an ester and the reaction is Curdling of milk called esterification. Ethanol reacts with ethanoic

acid in the presence of conc. H2SO4 to form ethyl 11.6.2 Physical properties ethanoate, an ester.

conc.H SO i) Ethanol is a colourless liquid, having a 2 4 C2H5OH + CH3COOH CH3COOC2H5 + H2O pleasant smell and a burning taste. Ethanol Ethanoic acid Ethyl ethanoate ii) It is a volatile liquid. Its boiling point is 780 C (v) Dehydrogenation: (351K), which is much higher than that of its corresponding alkane, i.e. ethane (Boiling When the vapour of ethanol is passed over Point = 184 K). heated copper, used as a catalyst at 573 K, it is dehydrogenated to acetaldehyde. iii) It is completely miscible with water in all Cu proportions. CH CH OH CH CHO + H 3 2 573K 3 2 Ethanol Acetadehyde 11.6.3 Chemical Properties (i) Dehydration (Loss of water) (vi) Combustion: Ethanol is highly inflammable liquid. It burns When ethanol is heated with con H2SO4 at 443K, it loses a water molecule i.e. dehydrated to with oxygen to form carbon dioxide and water.

form ethene. C2H5OH + 3O2 2CO2 + 3H2O Ethanol Carbon dioxide Conc.H2SO4 CH3CH2OH CH2 = CH2 + H2O 443K Ethanol Ethene 11.6.4 Uses of ethanol Ethanol is used (ii) Reaction with sodium: � in medical wipes, as an antiseptic. Ethanol reacts with sodium metal to form � as an anti-freeze in automobile radiators. sodium ethoxide and hydrogen gas. � for effectively killing micro organisms ↑ 2C2H5OH + 2Na 2C2H5ONa + H2 like bacteria, fungi, etc., by including it in sodium ethoxide many hand sanitizers.

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10th_Science_Unit-11.indd 164 21-02-2019 18:40:58 � as an antiseptic to sterilize wounds in (ii) It is sour in taste. hospitals. (iii) It is miscible with water in all proportions. � as a solvent for drugs, oils, fats, perfumes, (iv) Its boiling point is higher than the corresponding alcohols, aldehydes and dyes, etc. ketones. � in the preparation of methylated spirit (v) On cooling, pure ethanoic acid is frozen to (mixture of 95% of ethanol and 5% of form ice like flakes. They look like glaciers, methanol) rectified spirit (mixture of so it is called glacial acetic acid. 95.5% of ethanol and 4.5% of water), power alcohol (mixture of petrol and ethanol) 11.7.3 Chemical Properties and denatured spirit (ethanol mixed with (i) Reaction with metal: Ethanoic acid reacts pyridine). with active metals like Na, Zn, etc., to liberate � to enhance the flavour of food extracts, hydrogen and form sodium ethanoate. for example vanilla extract; a common 2CH3COOH + Zn → (CH3COO)2 Zn + H2 ↑ food flavour, which is made by processing vanilla beans in a solution of ethanol and 2CH3COOH + 2Na → 2CH3COONa + H2 ↑ water. (ii) Reaction with carbonates and bicarbonates: Ethanoic acid reacts with sodium carbonate and sodium bicarbonate, 11.7 ETHANOIC ACID (CH3COOH) which are weaker bases and liberates CO2, Ethanoic acid or acetic acid is one of the with brisk effervescence. most important members of the carboxylic 2CH COOH + Na CO → 2CH COONa + acid family. Its molecular formula is C H O . Its 3 2 3 3 2 4 2 CO ↑ + H O structural formula is 2 2

CH3COOH + NaHCO3 → CH3COONa + O

H CO2↑ + H2O

H C C OH (iii) Reaction with base: Ethanoic acid reacts H with sodium hydroxide to form sodium ethanoate and water. 11.7.1 Manufacture of ethanoic CH3COOH + NaOH → CH3COONa + H2O acid (iv) Decarboxylation (Removal of CO2): Ethanoic acid is prepared in large scale, When a sodium salt of ethanoic acid is by the oxidation of ethanol in the presence of heated with soda lime (solid mixure of 3 parts alkaline potassium permanganate or acidified of NaOH and 1 part of CaO), methane gas is potassium dichromate. formed. - KMnO4/ OH CH3CH2OH CH3COOH + H2O NaOH / CaO 2[O] CH COONa CH ↑ + Na CO Ethanol Ethanoic acid 3 4 2 3 11.7.4 Uses of ethanoic acid 11.7.2 Physical Properties Acetic acid, in lower concentration, is (i) Ethanoic acid is a colourless liquid having an used as a food additive, a flavoring agent and a unpleasant odour. preservative.

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10th_Science_Unit-11.indd 165 21-02-2019 18:40:58 Ethanoic acid is used 11.9 SOAPS AND DETERGENTS � in the manufacture of plastic. Soaps and the Detergents are materials that � in making dyes, pigments and paint. are used by us for cleaning purposes because � in printing on fabrics. pure water alone cannot remove all types of dirt � as a laboratory reagent. or any oily substance from our body or clothes. � for coagulating rubber from latex. They contain ‘surfactants’, which are compounds � in the production of pharmaceuticals. with molecules that line up around water to break the ‘surface tension’. Both of them having a different chemical nature. Soap is a cleaning 11.8 ORGANIC COMPOUNDS agent that is composed of one or more salts of IN DAILY LIFE fatty acids. Detergent is a chemical compound or a mixture of chemical compounds, which is Organic compounds are inseparable in used as a cleaning agent, also. They perform their human life. They are used by mankind or cleaning actions in certain specific conditions. associated at all stages of life right from one's You will learn more about this in detail, in the birth to death. Various classes of organic following units. compounds and their uses in our daily life as follows: 11.9.1 Soap Soaps are sodium or potassium salts of some Hydrocarbons long chain carboxylic acids, called fatty ­acids. ‹ Fuels like LPG, Petrol, Kerosene. Soap requires two major raw materials: i) fat ‹ Raw materials for various important and ii) alkali. The alkali, most commonly used synthetic materials. in the preparation of soap is sodium hydroxide.­ ‹ Polymeric materials like tyre, plastic Potassium hydroxide can also be used. A containers. ­potassium-based soap creates a more water-­ Alcohols soluble product than a sodium-based soap. Based ‹ As a solvent and an antiseptic agent. on these features, there are two types of soaps: ‹ Raw materials for various important A. HARD SOAP synthetic materials. Soaps, which are prepared by the Aldehydes saponification of oils or fats with caustic soda ‹ Formaldehyde as a disinfectant. (sodium hydroxide), are known as hard soaps. ‹ Raw materials for synthetic materials. They are usually used for washing purposes.

Ketones B. SOFT SOAP ‹ As a solvent. Soaps, which are prepared by the ‹ Stain Remover. saponification of oils or fats with potassium Ethers salts, are known as soft soaps. They are used for cleansing the body. ‹ Anaesthetic agents. ‹ Pain Killer. Manufacture of soap Esters KETTLE PROCESS: ‹ All the cooking oils and lipids contain This is the oldest method. But, it is still esters. widely used in the small scale preparation of

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10th_Science_Unit-11.indd 166 21-02-2019 18:40:58 soap. There are mainly, two steps to be followed These soaps possess the desirable properties of in this process. ordinary soaps and also can be used with hard i) Saponification of oil: water and in acidic solutions. These are salts of sulphonic acids or alkyl hydrogen sulphates The oil, which is used in this process, in comparison to soap, which are salts of is taken in an iron tank (kettle). The alkaline carboxylic acids. The detergents do not form solution (10%) is added into the kettle, a little precipitates with Ca2+ and Mg2+ present in hard in excess. The mixture is boiled by passing water. So, the cleansing action of detergents is steam through it. The oil gets hydrolysed after better than that of soaps. several hours of boiling. This process is called Saponification Preparation of detergents ii) Salting out of soap: Detergents are prepared by adding sulphuric Common salt is then added to the boiling acid to the processed hydrocarbon obtained mixture. Soap is finally precipitated in the tank. from petroleum. This chemical reaction result After several hours the soap rises to the top of the in the formation of molecules similar to the liquid as a ‘curdy mass’. The neat soap is taken fatty acid in soap. Then, an alkali is added to the off from the top. It is then allowed to cool down. mixture to produce the ‘surfactant molecules’, which do not bond with the minerals present in Effect of hard water on soap the hard water, thus preventing the formation of Hard water contains calcium and their precipitates. magnesium ions (Ca2+ and Mg2+) that limit In addition to a ‘surfactant’, the modern the cleaning action of soap. When combined detergent contains several other ingredients. with soap, hard water develops a thin layer They are listed as follows: (precipitates of the metal ions) called ‘scum’, which leaves a deposit on the clothes or skin i) Sodium silicate, which prevents the corrosion and does not easily rinse away. Over time, this and ensures that the detergent does not can lead to the deterioration of the fabric and damage the washing machine. eventually ruin the clothes. On the other hand, ii) Fluorescent whitening agents that give a glow detergents are made with chemicals that are not to the clothes. affected by hard water. iii) Oxygen bleaches, such as ‘sodium perborate’, enable the removal of certain stains from the Why ordinary soap is not cloth. suitable for using with hard iv) Sodium sulphate is added to prevent the water? caking of the detergent powder. Ordinary soaps when treated v) Enzymes are added to break down some with hard water, precipitate as salts of stains caused by biological substances like calcium and magnesium. They appear blood and vegetable juice. at the surface of the cloth as sticky grey vi) Certain chemicals that give out a pleasant scum. Thus, the soaps cannot be used smell are also added to make the clothes conveniently in hard water. fragrant after they are washed with detergents.

11.9.2 Detergents 11.9.3 Cleansing action of soap Development of synthetic detergents is A soap molecule contains two chemically a big achievement in the field of cleansing. distinct parts that interact differently with

167 Carbon and its Compounds

10th_Science_Unit-11.indd 167 21-02-2019 18:40:58 water. It has one polar ¾¾ do an effective and safe cleansing, end, which is a short keeping even synthetic fabrics brighter head with a carboxylate and whiter. group (–COONa) and one Biodegradable and Non-biodegradable non-polar end having detergents: the long tail made of the hydrocarbon chain. a) Biodegradable detergents: The polar end is hydrophilic (Water They have straight hydrocarbon chains, loving) in nature and this end is attracted which can be easily degraded by bacteria. towards water. The non-polar end is hydrophobic (Water hating) in nature and it is attracted towards dirt or oil on the cloth, Soap molucules but not attracted towards water. Thus, the Soap solutoin Dirty cloth hydrophobic part of the soap molecule traps the dirt and the hydrophilic part makes the Dirt entire molecule soluble in water. When a soap or detergent is dissolved in water, the molecules join together as clusters called ‘micelles’. Their long hydrocarbon chains attach themselves to the oil and dirt. The dirt is thus surrounded by the non-polar Hydrophilic head end of the soap molecules (Figure 11.3). The charged carboxylate end of the soap molecules makes the micelles soluble in water. Thus, the dirt is washed away with the soap. Aqueous soluon

Advantages of detergents over soaps Detergents are better than soaps because they: Hydrophobic tail ¾¾ can be used in both hard and soft water and can clean more effectively in hard water Figure 11.3 Cleansing action of soap than soap. ¾¾ can also be used in saline and acidic water. b) Non-biodegradable detergents: ¾¾ do not leave any soap scum on the tub or They have highly branched hydrocarbon clothes. chains, which cannot be degraded by bacteria. ¾¾ dissolve freely even in cool water and rinse freely in hard water. Disadvantages of Detergents ¾ ¾ can be used for washing woollen garments, 1. Some detergents having a branched hydro- where as soap cannot be used. carbon chain are not fully biodegradable by ¾¾ have a linear hydrocarbon chain, which is micro-organisms present in water. So, they biodegradable. cause water pollution. 2. They are relatively more expensive than ¾ ¾ are active emulsifiers of motor grease. soap.

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10th_Science_Unit-11.indd 168 21-02-2019 18:40:59 11.9.4 Comparison between soap and detergents

Soap Detergent

It is a sodium salt of long chain fatty acids. It is sodium salts of sulphonic acids.

– + – + Th e ionic part of a soap is –COO Na . Th e ionic part in a detergent is –SO 3Na .

It is prepared from animal fats or vegetable oils. It is prepared from hydrocarbons obtained from crude oil.

Its eff ectiveness is reduced when used in hard It is eff ective even in hard water. water.

It forms a scum in hard water. Does not form a scum in hard water.

It has poor foaming capacity. It has rich foaming capacity.

Soaps are biodegradable. Most of the detergents are non-biodegradable.

Have you noticed the term  Functional group may be defi ned as an "TFM" in soap atom or group of atom or reactive part which is responsible for the characteristic properties of the compounds  Ethanoic acid is most commonly known as acetic acid and belongs to a group of acids called carboxylic acids.  Acetic acid is present in many fruits and it renders a sour taste to those fruits.  Ethanol or ethyl alcohol or simply alcohol TFM means TOTAL FATTY MATTER. It is the one of the important factors to be is one of the most important members of considered to assess the quality of soap. A the family of alcohols. soap, which has higher TFM, is a good bathing  Th e slow chemical change that takes soap. place in complex organic compounds by the action of enzymes leading to the formation of simple molecules is called Points to Remember fermentation.  A group or class of organic compounds  Soaps are sodium or potassium salts of related to each other by a general molecular some long chain carboxylic acids. formula constitutes homologous series.   Th e IUPAC name of the any organic Detergents are sodium salts of sulphonic compound consist of three parts. acids. Th us instead of –COOH group in ROOTWORD, PREFIX and / or SUFFIX. soaps, detergents contain –SO3H group

169 Carbon and its Compounds

10th_Science_Unit-11.indd 169 21-02-2019 18:40:59 TEXTBOOK EVALUATION

I. Choose the best answer. 9. Which of the following statements is wrong 1. The molecular formula of an open chain about detergents? organic compound is C H . The class of the 3 6 a. It is a sodium salt of long chain fatty compound is acids a. alkane b. alkene b. It is sodium salts of sulphonic acids c. alkyne d. alcohol – + c. The ionic part in a detergent is –SO3Na 2. The IUPAC name of an organic compound is d. It is effective even in hard water. 3-Methyl butan-1-ol. What type compound II. Fill in the blanks it is? 1. An atom or a group of atoms which is a. Aldehyde b. Carboxylic acid responsible for chemical characteristics of an c. Ketone d. Alcohol organic compound is called ______. 3. The secondary suffix used in IUPAC 2. The general molecular formula of alkynes is nomenclature of an aldehyde is ______a. - ol b. – oic acid 3. In IUPAC name, the carbon skeleton of a c. - al d. - one compound is represented by ______4. Which of the following pairs can be the (root word / prefix / suffix) successive members of a homologous series? 4. (Saturated / Unsaturated) ______

a. C 3H8 and C4H10 compounds decolourize bromine water. b. C H and C H 2 2 2 4 5. Dehydration of ethanol by conc. Sulphuric c. CH and C H 4 3 6 acid forms ______(ethene/ ethane) d. C2H5OH and C4H8OH 6. 100 % pure ethanol is called ______5. C2H5OH + 3O2 → 2CO2 + 3H2O is a a. Reduction of ethanol 7. Ethanoic acid turns ______litmus to b. Combustion of ethanol ______c. Oxidation of ethanoic acid 8. The alkaline hydrolysis of fatty acids is d. Oxidation of ethanal termed as ______6. Rectified spirit is an aqueous solution which 9. Biodegradable detergents are made of contains about ______of ethanol ______(branched / straight) chain a. 95.5 % b. 75.5 % hydrocarbons c. 55.5 % d. 45.5 % 7. Which of the following are used as III. Match the following anaesthetics? Functional group - Benzene a. Carboxylic acids b. Ethers –OH c. Esters d. Aldehydes Heterocyclic - Potassium stearate 8. TFM in soaps represents ______Unsaturated - Alcohol content in soap Soap - Furan a. mineral b. vitamin c. fatty acid d. carbohydrate Carbocyclic - Ethene

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10th_Science_Unit-11.indd 170 21-02-2019 18:40:59 IV. Assertion and Reason: (ii) Evolution of carbon dioxide by the action Answer the following questions using the of ethanoic acid with NaHCO3. data given below: (iii) Oxidation of ethanol by acidified i) A and R are correct, R explains the A. potassium dichromate. ii) A is correct, R is wrong. (iv) Combustion of ethanol. iii) A is wrong, R is correct. 5. Explain the mechanism of cleansing action iv) A and R are correct, R doesn’t explains A. of soap. 1. Assertion: Detergents are more effective cleansing agents than soaps in hard water. VII. HOT questions Reason: Calcium and magnesium salts of 1. The molecular formula of an alcohol is detergents are water soluble. C4H10O. The locant number of its –OH 2. Assertion: Alkanes are saturated group is 2. hydrocarbons. (i) Draw its structural formula. Reason: Hydrocarbons consist of covalent bonds. (ii) Give its IUPAC name. (iii) Is it saturated or unsaturated? V. Short answer questions 2. An organic compound ‘A’ is widely used 1. Name the simplest ketone and give its as a preservative and has the molecular structural formula. formula C2H4O2. This compound reacts 2. Classify the following compounds based on with ethanol to form a sweet smelling the pattern of carbon chain and give their compound ‘B’. structural formula: (i) Propane (ii) Benzene (i) Identify the compound ‘A’. (iii) Cyclobutane (iv) Furan (ii) Write the chemical equation for 3. How is ethanoic acid prepared from ethanol? its reaction with ethanol to form Give the chemical equation. compound ‘B’. 4. How do detergents cause water pollution? (iii) Name the process. Suggest remedial measures to prevent this pollution? 5. Differentiate soaps and detergents. REFERENCE BOOKS

VI. Long answer questions 1. Organic chemistry - B.S.Bahl & Arun Bahl 1. What is called homologous series? Give any S.Chand publishers, New delhi. three of its characteristics? 2. Organic chemistry - R.T.Morrision & 2. Arrive at, systematically, the IUPAC name R.MN. Boyd - Prentice Hall Publishers. New Delhi of the compound: CH3–CH2–CH2–OH. 3. How is ethanol manufactured from sugarcane? 4. Give the balanced chemical equation of the following reactions: (i) Neutralization of NaOH with ethanoic acid.

171 Carbon and its Compounds

10th_Science_Unit-11.indd 171 21-02-2019 18:40:59 Ether Concept Map alcohol Ester Organic acid Carboxylic acids Functional Drugs Daily use group Ketones Fuel

Aldehydes Tyre

Alcohols Carbon Plastic and its compounds Saturated Open chain Root word compounds Unsaturated IUPAC Pre x

Classi cation Naming Sux

Common Carbo cyclic Source compounds name Closed chain compounds Hetero cyclic compounds

Organic Carbon and its ICT CORNER Compounds

Th e students can know about the Hydrocarbons, its formulae, descriptions and also in animated form.

Steps • Type the URL or use the QR code to access the application “Organic chemistry visualized / OCV” and install in the mobile. • Click ‘Content’ to view the list of Hydrocarbon. Explore about the hydrocarbons by clicking those. • On clicking ‘anim’ button, you can view the formulae of hydrocarbon as well as in animated form. • Click ‘Quiz’ to evaluate yourself in this topic.

Step1 Step2 Step3 Step4

URL: https://play.google.com/store/apps/details?id=com.budgietainment.oc or Scan the QR Code.

*Pictures are indicative only

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