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Home , Pentyl group, Preferred IUPAC name, Propyl group

Concepts in Chemistry

CHAPTER-IV

TRIVIAL OR COMMON SYSTEM OF NOMENCLATURE

Naming an on the basis of the rules recommended by IUPAC is absolutely essential for big and complex molecules. However, small molecules are more popularly addressed by their common names or the trivial or the primitive names. We already know before that IUPAC has accepted a few common names as official names e.g , etc. for some compounds and isopropyl, sec-butyl, tert-butyl etc. as some groups. A detailed logically genesis of the common system is discussed below. TYPES OF ATOMS: There are four types of carbon atoms. (i) Primary or 10 carbon atom: carbon atom attached with 3 or 4 H atoms. (ii) Secondary(sec-) or 20 carbon atom: carbon atom attached with 2 H atoms. (iii) Tertiary(tert-) or 30 carbon atom: carbon atom attached with 1 H atom (iv) Quaternary or 40 carbon atom: carbon atom attached with no H atom.

0 0 0 1 1 1 CH3 0 0 CH3 0 0 CH3 1 3 0 4 2 3 Example: H3CCH C CH2 CH 0 0 1 1 CH3 CH3 In the above example, all the carbon atoms have been assigned with their types.

SAQ IV.1. (i)Name the molecule in which a primary carbon atoms is linked with 4 H atom. (ii)Draw the structure and give the IUPAC name of the compound which contains one 40 and four 10 carbon atoms. TYPES OF GROUPS: In common system alkyl groups are prefixed with the symbols n-, iso, sec-, tert- and neo. While naming the alkyl group all the carbon atoms present in the alkyl group are counted. Numbering of carbon atoms is not done in this case like IUPAC system. (i) normal or n-alkyl group: If all the carbon atoms of the alkyl group are connected in straight chain and there is no branching, it is called n-alkyl group.

H3CCH2 CH2 H3CCH2 CH2 CH2 H3CCH2 CH2 CH2 CH2 n-propyl n-butyl n-pentyl or n-amyl (N.B: Note that methyl and ethyl groups are named as such; not as n-methyl and n-ethyl, because they do not have any other types like iso, sec- , tert- or neo) Nomenclature of Organic Compounds

H3C (ii) isoalkyl group: The group beginning with CH unit and other carbon atoms if H3C any are connected in straight chain with no further branching is called isoalkyl group.

H3C H3C H3C CH CH2 CH2 CH (isopropyl), CH CH2 (isobutyl) H3C H3C H3C isopentyl or isoamyl

(iii) secondary or sec-alkyl group: When one H atom is removed from a secondary carbon atom, a sec- alkyl group results. gives sec-butyl and gives sec-propyl groups.

0 2

H3CCH2 CH2 CH3 H3CCH2 CH CH3 H3CCH2 CH

butane sec-butyl CH3 In sec-alkyl group the unfulfilled valency of the alkyl group(shown by dash mark) is connected to that carbon atom which is linking with one H atom.

0 2 H3C CH H3CCH2 CH3 H3CCHCH3 H3C propane sec-propyl Note that sec- is same as isopropyl as it satisfies the requirements of both types. Between the two names isopropyl is more popular and widely used. Note also that sec-alkyl group is restricted to sec-butyl only because larger sec-alkyl groups do not have unique structure. For example, sec- can have two different structures which can be obtained from by removing one H atom from C-2 and C-3. But butane gives only one sec- as C-2 position is unique. (iv) tertiary or tert-alkyl group: When one H atom is removed from a tertiary carbon atom, a tertiarty or tert- alkyl group results.

CH3 CH3 CH3 CH3 0 0 3 3 H3CCH H3CC H3C CH2 CH H3C CH2 C CH3 CH3 CH3 tert-pentyl CH3 tert-butyl In tert-butyl group the unfulfilled valency of the alkyl group(shown by dash mark) is connected to that carbon atom which does not link with any H atom. The use of tert-alkyl group is limited to tert-butyl and tert-pentyl groups only as for higher tert-alkyl groups unique structures are not possible. (v) neopentyl group: The alkyl group beginning with the following part structure(I) and other carbon atoms if any are connected in straight chain is called neoalkyl group. Concepts in Chemistry

CH3 CH3 CH3 H C C CH (neopentyl) H C C CH CH (neohexyl) H3CCCH2 (I) 3 2 3 2 2 and CH3 CH3 CH3 so on Note that while iso and neo prefixes are integrated with the names of the alkyl groups, n-, sec- and tert- prefixes remain separated from alkyl groups by a hyphen. SAQ IV.2: Draw the structures of the following alkyl groups (i)n-hexyl (ii)isohexyl (iii)neoheptyl NAMING OF COMPOUNDS USING COMMON OR TRIVIAL SYSTEMS: 1. : (i) normal or n-: When the carbon atoms are connected in straight chain and there is no branching, it is called a n-alkane. In other words one one H atom is attached with a n- alkyl group it becomes a n-alkane.

H3CCH2 CH2 CH3 (n-butane), H3CCH2 CH2 CH2 CH3 (n-pentane) (ii) isoalkane: When one H atom is attached with an isoalkyl group, an isoalkane results.

H3C H3C CH CH3 (isobutane) CH CH2 CH3 () H3C H3C (iii) neoalkane: When one H atom is attached with a neoalkyl group, a neoalkane results.

CH3 CH 3 H CCCH H CCCH CH 3 3 (neopantane) 3 2 3 (neohexane) CH3 CH 3 IMPORTANT: The names isobutane, isopentane and neopantane have been accepted as sytstematic IUPAC names for those alkanes. OLEFINES (): The first member of is called and all other alkenes are expressed as substituted . Monosubstituted ethylene: If there is one alkyl attached to any carbon atom of the C=C in place of one H atom, then it is called alkylethylene. It is a monosubstitued alkene.

: H2CCH2 ethylene(ethene); H2CCHCH3 propylene or methyl ethylene() Disubstituted ethylene Disubstituted alkenes are classifed as (i)symmetrical or sym-alkene and (ii)unsymmetrical or unsym-alkene. Nomenclature of Organic Compounds Symmetrical alkene: If one H atom from each of the two doubly bonded carbon atoms is substituted by same alkyl groups, it is a symmetrical alkene. Unsymmetrical alkene: If two H atoms of any one doubly bonded carbon atom are substituted by two same alkyl groups, it is an unsymmetrical alkene. The IUPAC names have been given inside parentheses for comparison.

CH3 CH CH CH3 CH3 CCH2 CH3 sym-dimethylethylene unsym-dimethylethylen (but-2-ene) (2-methylpropene) Unsym-dimethylethylene(2-methylpropene) is also called isobutene or isobutylene. : The first member of alkyne is called and all other alkenes are expressed as substituted - (i)monosubstituted- if one H atom is replaced by an alkyl group or (ii)disubstituted- if both the H atoms are replaced by alkyl groups

H3C CH CCH HC CH H3CC CH H3CCCCH3 acetylene methylacetylene dimethylacetylene H3C isopropylacetylene SAQ IV.3: Draw the structures of the following compounds. Also give their IUPAC names. (i)isohexane (ii)neoheptane (iii)sec-butylethylene (iv)sym-diisopropylethylene (v)tert-butylacetylene (vi)ethylisobutylacetylene (vii)n-heptane ALKYL HALIDE(): The are called alkyl halides in the common system. First the name of alkyl group according to common system is written which is followed by the term halide(, chloride, bromide, iodide) with a space in between.

CH3 H3C CH Cl H3C C Br H3CCH2 CH2 I

H3C CH3 isopropyl chloride tert-butylbromide n-propyl iodide (2-chloroprapane) (2-bromo-2-methylpropane) (1-iodopropane) SAQ IV.4: Give the common names of the following alkyl halides, also write their IUPAC names.

H3C CH CH2 Br (i)CH3Br (ii)CH3-CH2-Cl (iii) (CH3)3C-I (iv) H3C SAQ IV.5: Draw the structures of the following and also give their IUPAC names. (i)sec-butyl chloride (ii)neopentyl iodide (iii)isohexylbromide (iv)tert-pentyl chloride (v) n-propyl iodide : In common system, an alcohol is named as alkyl alcohol. First the name of the alkyl group is written according to common system, followed by the term alcohol with a space in between. Concepts in Chemistry

CH3 H3C CH OH H3CCH2 CH OH H3CC CH2 OH CH3 H3C CH3 sec-butyl alcohol neopentyl alcohol (propan-2-ol) (butan-2-ol) (2,2-dimethylpropan-1-ol) THIOALCOHOL: In common system thioalcohol is named as alkyl mercaptan. First the name of the alkyl group is written according to common system, followed by the term mercaptan with a space in between.

H3C 3 SH 2 SH H3C

CH H3C 3 1 sec-butyl mercaptan(butane-2-) isopropyl mercaptan (propane-2-thiol); SALT OF ALCOHOL: RONa or ROK are the salts of alcohol which are named as metal alkoxides. The of the alkyl group is used to name the alkoxide.

H3C O Na sodium isopropoxide(sodium propan-2-olate); H3C

CH3CH2OK potassium ethoxide (potassium ethanolate) SAQ IV.6: Give the names of the following according to common system.Also give their IUPAC names.

(i) CH3-CH2-OH (ii)CH3-OH (iii) CH3-CH2-CH2-OH (iv)CH3-CH(OH)-CH2-

CH3 (v)(CH3)3COH (vi)(CH3)2CHCH2CH2OH SAQ IV.7: Draw the structures of the following . Also give their IUPAC names, (i) tert-pentyl alcohol (ii) n-butyl alcohol (iii) isopropyl alcohol (iv)isobutyl mercaptan (v) sodium tert-butoxide (vi)potassium methoxide : is named as alkyl alkyl ketone or dialkyl ketone having a space between any two words.The two alkyl groups attached to the are written first in alphabetical order followed by the term ketone. If the two alkyl groups are same then we write dialkyl ketone. Note that the carbonyl carbon is excluded while naming the two alkyl groups and the term ketone in the name signifies the carbonyl carbon atom.

O dimethyl ketone or (propanone) CH3 CCH3

The carbonyl(C=O) group is connected to two methyl(CH3)groups, hence the name dimethyl ketone. ACETONE is its most popular name and has been accepted by IUPAC as official name. Nomenclature of Organic Compounds

O O O CH3 CH3

H3CCH2 C CH3 H3CCH2 CH C CH3 H3CC C C CH3 CH CH3 CH3 3 ethyl methyl ketone sec-butyl methyl ketone ditert-butyl ketone (butan-2-one) (3-methylpentan-2-one) (2,2,4,4-tetramethylpentan-3-one) SAQ IV.8: Draw the structures and give IUPAC names of the following compounds. (i) ethyl isobutyl ketone (ii)isopentyl n-propyl ketone (iii)disec-butyl ketone

ALDEHYDE: have typical common names. Try to remember them.

O O O O

HCH H3CC H H3C H2CC H H3C CH2 H2CC H propionaldehyde butyraldehyde (methanal) (ethanal) (propanal) (butanal) The common names of the first four aldehydes are so widely popular that they are also regarded as official names by IUPAC.

SAQ IV.9: Write the structure and IUPAC name of isobutyraldehyde

CARBOXYLIC ACIDS(FATTY ACIDS) Carboxylic acids have similar names as aldehydes. They were called fatty acids because they were first derived from natural fats. O O O O

HCOH H3CC OH H3C H2CC OH H3C CH2 H2CC OH formic acid acetic acid n-butyric acid (methnoic acid) (ethanoic acid) (propanoic acid) (butanoic acid)

The first four common names are also regarded as official names by IUPAC. The common names of straight chain carboxylic acids containing greater number of carbon atoms are given below.

C5- valeric acid(pentanoic acid) , C6-caproic acid(hexanoic acid), C8-caprylic acid(octanoic acid),

C10- capric acid(decanoic acid), C12-lauric acid(dodecanoic acid), C14-myristic acid(tetradecanoic acid), C16-palmitic acid(hexadecanoic acid), C18-stearic acid(octadecanoic acid), C20-arachidic acid(eicosanoic acid), C22-behenic acid(docosanoic acid), C24-lignoceric acid(tetracosanoic acid),

C26-cerotic acid(hexacosanoic acid), C30-melissic acid(tricontanoic acid), C7-oenanthylic acid(hepatanoic acid), C9-pelargonic acid(nonanoic acid). (NB: The students are advised not to remember these names. These are given only for referenece)

CH3

2 COOH H3C COOH 3 1 O H2C CH3 (pyruvic acid) H3C COOH pivalic acid Concepts in Chemistry Pivalic acid(2,2-dimethylpropanoic acid) and acrylic acid(prop-2-enoic acid) are accepted also as the IUPAC names. Pyruvic acid is named as 2-oxopropanoic acid by IUPAC system. SAQ IV.10: Write the structures of the following and also give their IUPAC names. (i) (ii)valeric acid (iii) isovaleric acid (iv)palmitic acid

ESTERS: -ate is used in place of -ic as suffix with the common name of the acid . Look at the examples.

O methyl (methyl ethanoate). Here, the name of the acid in H3CCO CH3 common system is acetic acid hence the is named as acetate. Similary, other have the parent name as formate, propionate, butyrate, valerate etc. The names formate, acetate, propionate and butyrate are also regarded as official IUPAC names. In fact, the first four common names of all the derivatives of carboxylic acids are regarded as alternative official names by IUPAC.

O O O CH 3 H CCH CH C OCH CH CH HCOCH H3CCH2 C OCHCH 2 CH 3 3 2 2 2 2 3 CH 3 CH 3 n-propyl butyrate isopropyl formate sec-butyl propionate (isopropyl methanoate) (sec-butyl propanoate) (n-pro pyl bu tan oate) SAQ IV.11: Draw the structures of the following and also give their IUPAC names. (i)isobutyl acetate (ii)tert-butyl valerate (iii)neopentyl laurate (iv)sec-butyl isobutyrate (v)n-amyl formate

ACID : - is used as suffix with the common name of the acid.

O O (methanamide), (ethanamide) HC NH2 CH3 CNH2

Higher amides are propionamide(C3), butyramide(C5), valeramide(C5) and so on. ACID CHLORIDE: -yl chloride is used in place of -ic chloride as suffix with the common name.

O (ethanoyl chloride). Similarly, for higher members the CH3 CCl names are propionyl chloride, butyryl chloride, valeryl chloride and so on. SALTS OF : -ate is used as suffix in place of -ic with the common name of acid.

O O - + O - + - 2+ H C C O Ca H3CCO Na HCO K 3 2 sodium acetate potassium formate calcium acetate (sodium ethanoate) (potassium methanoate) (calcium ethanoate) Nomenclature of Organic Compounds ACID ANHYDRIDE: Anhydride is used as the suffix with the common name.

OO acetic anhydride(ethanoic anhydride) - symmetrical anhydride H3CCOC CH3

O O O O H CCOCCH CH H CCHCH C OCCH CH 3 2 3 3 2 2 2 3 unsym. anhydride acetic propinoic anhydride butyric propionic anhydride (ethanoic propanoic anyhydride) (butanoic propanoic anhydride) ALKYL (ALKANENITRILE): Name of the alkyl group in common system is written first which is followed by the suffix cyanide with a space in between. Note that cyanide carbon is not included while naming the alkyl group. In IUPAC naming the cyanide carbon is included in the name(alkanenitrile).

CH3 CN CH3 CH2 CN H3CCH2 CH2 CN methyl cyanide ethyl cyanide n-propyl cyanide () (propiononitrile) (butyronitrile) (ethanenitrile) (propanenitrile) (butanenitrile)

SAQ IV.12: Give the structures and IUPAC names in case of the following. (i)isopropyl cyanide (ii)tert-butyl cyanide (iii)potassium isobutyrate (iv)butyric anhydride

α, β, γ....system of naming : In case of , carboxylic acid and its derivatives this system of naming is followed. The carbon atom adacent to the is called alpha(α) carbon, the subsequent atoms are called beta(β), gamma(γ), delta(δ). The attached to those carbon atoms are written first with the prefix α, β, γ... which are followed by the name of the parent compound in the common system.

    CCCCCOOH

CH OH O Br CH3 3 H C C CH C H CH2 CH COOH 3 CH3 β-bromo-α-methylpropionic acid α-hydroxy-β,β-dimethylbutyraldehyde SAQ.IV.13: Give the structures and IUPAC names of the following. (i)β-amino-α-methyl propionamide (ii)isoproyl α-chloro acetate (iii)β,β-dimethyl butyryl chloride (iv)γ-bromo-α,β-dimethylvaleric acid

AMINES: 1. 10 : Primary amine is named as alkyl amine. The common name of the alkyl group is written first followed by the term amine. Concepts in Chemistry

CH3 H3C CH NH2 H3CCH2 CH NH2 H3CCCH2 NH2 H C 3 CH3 CH3 isopropyl amine sec-butyl amine neopentyl amine (propan-2-amine) (butan-2-amine) (2,2-dimethylpropan-1-amine) 2. 20 : Sec-amines are named as alkyl alkyl amine when two alkyl groups are different and dialkyl amine when the two alkyl groups are identical. Note that the common names of alkyl groups are used.

H C CH3 H3C 3 CH CH NH CH CH CH NH CH2 CH3 2 2 H C H3C 3 CH3 ethyl isopropyl amine diisobutyl amine (N-ethylpropan-2-amine) (N-isobutyl-2-methylpropan-1-amine) 3. 30 amines: Tert-amines are named as alkyl alkyl alkyl amine when the three alkyl groups are different and dialkyl alkyl amine when two alkyl groups are identical and the third is different and trialkyl amine when the three alkyl groups are identical.

CH3 CH CH H3C 3 3 CH2 CH CH2 H3C H3CCH2 CH NCH3 CH N CH3 H3CCH2 N CH2 CH3 CH3 H3C sec-butyl ethyl methyl amine diisopropyl methyl amine triethyl amine (N-ethyl-N-methylbutan-2-amine) (N-isopropyl-N-methylpropan-2-amine) (N,N-diethylethanamine)

ETHERS: are named as alkyl alkyl or dialkyl ether depending on whether the alkyl groups are respectively different or same. The common names of alkyl groups are used.

H3C CH OCH2 CH3 H3CCH2 CH2 OCH2 CH2 CH3 H3C ethyl isopropyl ether di n-propyl ether (2-ethoxypropane) (1-propoxypropane)

CH3 O

H3C

CH3 H3C CH3

sec-butyl tert-butyl ether (2-tert-butoxybutane) Nomenclature of Organic Compounds IMPORNTANT: The common names of ethers involving simple common alkyl groups like isopropyl, sec-butyl, isobutyl, tert-butyl, neopentyl etc. as discussed above are sometimes used as the preferred official names by IUPAC.

SAQ IV.14: Give the structures and IUPAC names of the following. (i)tert-butyl amine (ii)tert-pentyl n-propyl amine (iii)trisec-butyl amine (iv)ethyl diisopropyl amine(v)methyl neopentyl ether (v)disec-butyl ether

PRACTICE QUESTIONS 1. Write the structures of the following compounds. Also give their IUPAC names. (i) n-butyl chloride (ii)sec. butyl alcohol (iii)Isopentane (iv)n-hexane (v)tert. butyl bromide (vi)n-pentyl alcohol (vii)diethyl ketone (viii)neohexane (ix) neopentyl chloride (x)n-propyl formate (xi)Isobutene (xii)dimethyl acetylene (xiii)isopropylbutyrate (xiv)α-methyl-β-hydroxyvaleric acid (xv)ethyl tert-pentyl ether (xvi)isobutyl neopentyl amine (xvii)triisopropyl amine (xviii)β-bromopivalic acid (xix)calcium α-methylpropionate (xx)α-methylbutyric anhydride 2. Give the structural formula and IUPAC names of the following. (a)isobutyl chloride (b)methyl neopentyl amine (c)acetamide (d)α-chlorobutyraldehyde (e)tert-butyl ethyl ketone (f)disec-butyl ether (g)isopropyl alcohol (h)N-sec- butyl formamide (i)isobutane (j)tert-pentyl acetylene (k)β-methyl butyramide (l)isopentyl bromide (m)diethyl isopropyl amine (n)trimethyl amine (o)isohexyl acetate 3.: Give the structure and IUPAC name of the following. (a)vinyl chloride(b)allyl ethyl ether (c)benzyl chloride (d)n-hexyl alcohol (e)cyclobutyl methyl amine (f)but-2-enyl chloride (g)propargyl bromide (h)ethylidene chloride (i)isopropylidene chloride (j)ethylene dichlorde (k)α-cyclohexyl acetaldehyde (l)allyl benzyl ether (m)m-hydroxyphenyl isopropyl amine (n)1,1,3-trimethylbutyl n-butyl ether (o)sodium laurate 4. Write both common and IUPAC names of the following.

CH3 H C 3 CH3 CH3 H3C H3C O CH3 CH3 N

H3C (i) H3C (ii) (iii) CH3 H C 3 CH3 CH3 O H3C H3C

H3C CH3 CH3

CH3 H3C

H3C H (iv) (v)

CH3 CH3 CH3 O Concepts in Chemistry

H3C H3C OH Br

(vi) H C (vii) 3 H3C CH 3 CH3 RESPONSE TO SAQs

CH3

H3C CH3 SAQ.IV.1: (i) CH4() (ii) (2,2-dimethylpropane) CH3

H3C CH CH2 CH2 CH2 SAQ.IV.2: (i) CH3 CH2 CH2 CH2 CH2 CH2 (ii) H3C

CH3 CH CCHCH CH (iii) 3 2 2 2 CH3

CH3 3 H3C CH3 1 5 2 4 2 3 H3C 1

CH3 4 CH3 SAQ.IV.3: (i) (ii) CH3 5 2-methylpentane 2,2-dimethylpentane

H3C H3C CH3

234 5 H3C 3 CH2 5 1 H C 2 3 CH3 (iii) 4 (iv) 1 6 3-methylpent-1-ene 2,5-dimethylhex-3-ene

CH3 23 4 5 CH3 H C 3 2 CH 6 3 H3C 4 1 1 CH3 7 (v) CH3 (vi) 3,3-dimethylbut-1-yne 6-methylhept-3-yne

(vii) CH3-(CH2)5-CH3 (heptane) SAQ.IV.4: (i)methyl bromide(bromomethane)(ii)ethyl chloride(chloroethane) (iii)tert- butyl iodide(2-iodo-2-methylpropane) (iv)isobutyl bromide(1-bromo-2-methylpropane)

CH3 CH3 H3C CH CCHI SAQ.IV.5: (i) Cl (ii) 3 2 (1-iodo-2,2-dimethylpropane) 2-chlorobutane CH3 Nomenclature of Organic Compounds

CH3 CH3 3 H C 2 4 2 Br 3 4 Cl 3 1 H3C H3C (iii) 5 (iv) 1 (v) 1-bromo-4-methylpentane 2-chloro-2-methylbutane

CH3 CH2 CH2 I 1-iodopropane

SAQ.IV.6: (i)ethyl alcohol() (ii)methyl alcohol() (iii) n-propyl alcohol(propan-1-ol) (iv)sec-butyl alcohol(butan-2-ol) (v)tert-butyl alcohol (2-methylpropan-2-ol (vi)isopentyl alcohol(3-methylbutan-1-ol) SAQ.IV.7:

CH3 OH 3 2 H3C 4 OH OH H3C H3C H C CH (i) 1 (ii) (iii) 3 3 butan-1-ol 2-methylbutan-2-ol propan-2-ol

H C 3 CH3

H3C ONa (iv) (v) (vi)CH3OK

H3C SH CH3 2-methylpropane-1-thiol sodium 2-methylpropan-2-olate postassium methanolate SAQ.IV.8:

H3C O 8 CH3 3 CH3 6 7 5 1 3 H3C 5 6 4 2 1 4 H C 2 3 CH (i) 3 (ii) O 5-methylhexan-3-one 7-methyloctan-4-one

CH3 CH3 CH H3C 3

(iii) O 3,5-dimethylheptan-4-one

H3C

CHO SAQ.IV.9: H3C 2-methylpropanal Concepts in Chemistry

SAQ.IV.10:

H C 3 H3C COOH 32 H C COOH H3C 3 H3C COOH (i) (ii) (iii) 4 1 pentanoic acid 2-methylpropanoic acid 3-methylbutanoic acid

(iv)CH3-(CH2)14-COOH(hexadecanoic acid) SAQ.IV.11:

O O CH H3C 4 2 3 H3C 3 1 5 CH3 O O CH3 H C (i)H3C (ii) 3 isopropyl acetate tert-butyl pentanoate

CH3 O H CCCH OC(CH ) CH (iii) 3 2 2 10 3 (neopentyldodecanoate) CH3

H3C O CH 3 3 O 21 CH 3 CH3 O H O (iv) H3C (v) sec-butyl 2-methylpropanoate pentyl formate

(N.B: Note that acetate and formate are the IUPAC accepted names for ethanoate and methanoate respectively) SAQ.IV.12:

H3C 3 CH3 2 CN 1 2 H3C H3C CN (i) (ii) 3 1 (2,2-dimethylpropanenitrile or pivalonitrile)

2-methylpropanenitrile CH3

O O CH3 - + CH COOK H3C O CH3 (iii) CH3 (iv) potassium 2-methylpropanoat butanoic anhydride Nomenclature of Organic Compounds SAQ.IV.13:

O CH3 Cl NH2 CH3 O CH3 (i) CH2 CH C NH2 (ii) O 3-amino-2-methylpropanamide isopropyl chloroacetate

CH3

Br CH3 CH3 H3C Cl

H3C COOH CH3 (iii) O (iv) 4-bromo-2,3-dimethylpentanoic acid 3,3-dimethylbutanoyl chloride

SAQ.IV.14:

CH CH CH CH3 3 3 3 3 H3C H3C H3C CH CH NCHCH2 CH3 H C 2 NH 4 NH 2 (i) 3 2 (ii) 3 2 (iii) H3CCHCH 2 CH3 CH3 CH3 1 1 N,N-disec-butylbutan-2-amine 2-methylpropan-2-amine 2-methyl-N-propylbutan-2-amine

CH CH 3 1 3

CH 2 2 CH 3 H3C O CH3 H 3C 3 CH NCH (iv) (v) CH3 H 3C CH 3 N-ethyl-N-isopropylpropan-2-amine 1-methoxy-2,2-dimethylpropane

(vi)CH3CH2(CH3)OCH(CH3)CH2CH3 (2-sec-butoxybutane)

ANSWER TO PRACTICE QUESTIONS

1. (i) H3CCH2 CH2 CH2 Cl (1-chlorobutane)

H C CH3 3 (ii) (butan-2-ol) (iii) CH CH2 CH3 (2-methylbutane) H3CCH2 CH OH H3C

CH3

H3CCBr (iv) H3CCH2 CH2 CH2 CH2 CH3 (hexane) (v) (2-bromo-2-methylpropane) CH3

(vi) H3CCH2 CH2 CH2 CH2 OH (pentan-1-ol)

O (vii) (pentan-3-one) H3CCH2 CCH2 CH3 Concepts in Chemistry

CH3 (viii) H3CCCH2 CH3 (2,2-dimethylbutane) CH3

CH3 (ix) H3CCCH2 Cl (1-chloro-2,2-dimethylpropane) CH3

O (x) (propyl methanoate or propyl formate) HCOCH2 CH2 CH3

H3C C CH2 (xi) (2-methylpropene) (xii) H3CC C CH3 (but-2-yne) H3C

CH H3C 2 O 3 4 (xiii) 3 1 (isopropyl butanoate or butyrate) O CH3

CH3

OH (xiv)H3C (3-hydroxy-2-methylpentanoic acid) OH O

CH3 CH3 (xv)H3C O (2-ethoxy-2-methylbutane) CH3

CH3 H3C NH 3 21 (xvi) CH3 (N-isobutyl-2,2-dimethylpropan-1-amine) H C 3 CH3

CH H3C 3 H3C CH3 (xvii) N (N,N-diisopropylpropan-2-amine) CH H3C 3

H3C (xviii)Br (3-bromo-2,2-dimethylpropanoic acid) COOH CH3

CH3 (xix) (calcium 2-methylpropanoate) H3CCHCOO Ca 2 Nomenclature of Organic Compounds

(xx) CH3CH2CH(CH3)COOCOCH(CH3)CH2CH3 (2-methylbutanoic anhydride)

2. (a) (CH3)2CHCH2Cl(1-chloro-2-methylpropane) (b)MeNHCH2C(CH3)3 (N,2,2- trimethylpropan-1-amine) (c) CH3CONH2(ethananmide or acetamide)

(d)CH3CH2CH(Cl)CHO (2-chlorobutanal) (e)(CH3)3CCOCH2CH3(2,2-dimethylpentan-

3-one) (f)[CH3CH2CH(CH3)]2O (2-sec-butoxybutane)

(g)(CH3)2CHOH(propan-2-ol) (h)HCONHCH(CH3)CH2CH3(N-sec-butylformamide or methanamide)

(i) (CH3)3CH(2-methylpropane) (j) CH CC(CH3)(CH3)CH2CH3 (3,3-dimethylpent-1-yne)

(k) CH3CH(CH3)CH2CONH2(3-methylbutanamide) (l)(CH3)2CHCH2CH2Br(1-bromo-3- methylbutane)

(m) (CH3)2CHN(C2H5)(C2H5)(N,N-diethylpropan-2-amine)

(n)(CH3)3N(N,N-dimethylmethanamine)

(o) CH3COOCH2CH2CH2CH(CH3)2

3. (a) CH2=CHCl (chloroethene) (b)CH2=CHCH2OCH2CH3(3-ethoxypropene)

(c)C6H5CH2Cl(chloromethylbenzene) (d)CH3(CH2)4CH2OH(hexan-1-ol)

NH CH3 (e) (N-methylcyclobutanamine) (f)CH3CH=CHCH2-Cl(1-chlorobut-2-ene)

Cl (g) HC C CH Cl (3-chloropropyne) (h) H CCH (1,1-dichloroethane 2 3 Cl

H3C Cl C (i) (2,2-dichloropropane) (j) ClCH2-CH2Cl(1,2-dichloroethane H3C Cl

(k) (C6H11)CH2CHO (2-cyclohexylethanal)

(l) PhCH2OCH2CH=CH2([(allyloxy)methyl] or 3-benzyloxypropene) HO

CH3 (m) [3-(isopropylamino)]

NH CH3

CH3

O

(n)H C (2-butoxy-2,4-dimethylpentane) 3 CH3

CH3 CH3

(o)CH3(CH2)10COONa (sodium dodecanoate) 4. (i)isoamyl tert-pentyl ether [1-(tert-pentoxy)-3-methylbutane or 1-(1,1-dimethylpropyl)-3- methylbutane] (ii) sec-butyl tert-butyl ethyl amine[N-(tert-butyl)-N-ethylbutan-2-amine (iii)isopropyl neopentyl ketone [2,5,5-trimethylhexan-3-one] (iv) α-isopropyl-β- methylbutyraldehyde[2-isopropyl-3-methylbutanal] (v)isobutyl tert-pentyl acetylene[2,6,6- trimethyloct-4-yne] (vi) neohexyl alcohol[3,3-dimethylbutan-1-ol] (vii)neoheptyl bromide[1-bromo- 4,4-dimethylpentane] Concepts in Chemistry

PREFERRED IUPAC NAMES(PIN)

The 1993 recommendations of IUPAC have allowed the use of more than one names for a single structure provided the different names can unambiguously represent the same structure. Names based on older IUPAC rules and also names from tradional origin could be officially used as general IUPAC names of a compound. However out of these names the one which is based strictly on the latest IUPAC recommendations(2004) is called the PREFERRED IUPAC NAME(PIN). Other names than the PIN if any can also be used as official names as long as the names respresent the same structure without any ambiguity. This popular stand taken by IUPAC is based on the principle that a single organic structure can have more than one IUPAC names but a single name cannot represent more than one structure. A few examples will make this point clear. Below you find a table giving the PIN and other IUPAC names of a few compounds.

Name of the Preferred Other compound IUPAC name(PIN) IUPAC name O acetone propan-2-one H 3CCCH 3

OH but-3-en-2-ol 3-buten-2-ol H3CCHCH CH 2

H2CCHCH2 CH3 but-1-ene 1-butene H2 H2 H2 1-ethoxypropane ethyl propyl ether H3C C O C C CH3

O H 3C

CH C CH 3 3-methylbutan-2-one isopropyl methyl ketone H 3C

CH3COOH acetic acid ethanoic acid

CH3CN acetonitrile ethanenitrile

NC-CH2-CH(CN)CH2CN propane-1,2,3-tricarbonitrile 3-cyanopentane dinitrile HCHO formaldehyde methanal

CH2(OH)CH(OH)CH2OH propane-1,2,3-triol

In the chapters I, II and III of the organic nomenclature part of this book, the PINs are highlighted for structures carrying more than one IUPAC names. One thing you bear in mind that whatever be the name of a compound if that name can generate an unambiguous structure, the name has to be accepted with due honour even if that may not be preferred IUPAC name. Nomenclature of Organic Compounds

MISCELLANEOUS PRACTICE QUESTIONS Give the preferred IUPAC names(PIN) and other names if any for the following compounds.

1. CH3-O-CH2-CH2-O-CH2-CH2-O-CH2-CH3

H2 O O C CH C CH3 3 H2 CHO O

2. 3. 4. S

CHO HO O OH

O

CH3 CO 5. HO 6. 7.

H3C O O

CH3 CH3

H C 8. 3 9. Cl

CH3

O

O CH3 10. 11. 12. CHO H3C

O

NH NH 13. 14. NH H3C CH3

O

15. 16. OH 17. Cl HC O Br Concepts in Chemistry

4 OH 5 3

CH3

CH3

18. 19. 20. 6 2 O O O

NH CH3 O 1

CH3 OH

21. CH3 22.

O OO CH3

CH3

CH3

23. 24. H3C CH3 25.

CH 3 H3C

CH3

CH3

OH

O 26. 27. H3C OH

H3C CH3

CH3 O

28. O 29.

H3C CH3

CH3

CH3 CH2 CH3

30. CH2 31. 32.

H2C Nomenclature of Organic Compounds

SH O N 6 OH CH3 5 1 O

33. O 34. 35. 4 2 CH3 3 CH3

O OH

Br CH3

H C 1 3 Cl 2 S 36. 37. 5 3 Br CH3 Br 4

COOH HO CH3 Br

38. 39. CH3

NO HO 2

CH3

3 4

CH3 40. 41. 2 H2C NH 5

N H 1

CH3

O 4

5 3 O

O 42. 6 2 43. CH H C N 3 3 1

CH3

CH3

CH3

44. 45.

CH3 O CH3 Concepts in Chemistry

Answers to Miscellaneous Practice Questions

1. 1-ethoxy-2-(2-methoxyethoxy) (PIN)/2,5,8-trioxadecane 2. propyl 4-hydroxybenzoate 3. phthalaldehyde(PIN)/benzene-1,2-dicarbaldehyde 4. 4-methylbenzenesulfonic acid(PIN)/p-toluenesulfonic acid 5.4-isopropylcyclobut-2-en-1-ol(PIN)/ 4-isopropyl-2-cyclobuten-1-ol 6. cyclohexylidenemethanone 7. cyclohexane-1,3,5-trione 8. 1-tert-butyl-4-cyclopropylcyclohexane 9. 3-chloro-6-ethylbicyclo[3.2.0]heptane 10. (2E,4E)-hexa-2,4-diene (if the groups lie on the opposite sides, it is called E(trans) and the groups lie on the same side it called Z(cis). In this case, at each C=C, the two groups connected lie opposite to each other. More about E and Z, you will know in the chapter stereoisomerism not given in this book) 11. 7-oxabicyclo[4.1.0]heptane(PIN)/1,2-epoxycyclohexane 12. 2-oxocyclohexanecarbaldehyde 13. N-methyl-N’-propylmethanediamine 14. N-phenylcyclohexanecarboxamide 15. 5-bromo-6-chlorocyclohex-1-en-3-yne 16.pent-4-yn-1-ol 17. dioxane(PIN)/1,4- dioxacyclohexane 18. -2,5-dione(PIN)/maleic anhydride 19. 3-(isopropylamino)-2-methylcyclohexanol 20.3,4-dihydro-2H-pyran(PIN)/oxacyclohex-2- ene 21. 3-(methoxymethoxy)propanoic acid 22. (1R,2R)-1,2-dimethylcyclohexane(PIN)/ trans-1,2-dimethylcyclohexane ( when two substituents remain on opposite sides i.e away from each other it is called trans . 1R, 2R refer to configurational identity of the carbon atoms which will not to be discussed here) 23. (1R,2S)-1,2-dimethylcyclobutane(PIN)/cis-1,2- dimethylcyclobutane( when two substitutents remain on the same side i.e close to each other, it is called cis isomer. 1R, 2S refers to configurational identitity of carbon atoms, not to be discussed here) 24. (2Z)-4-methylpent-2-ene(PIN)/cis-4-methylpent-2-ene (when branches lie on the same same side of the C=C, it is called trans Z or cis isomer) 25. (2E)-pent-2-ene(PIN)/trans-pent-2- ene(when branches like on the opposite side of the C=C, it is called E or trans isomer) 26. (2E)-3,7-dimethylocta-2,6-dien-1-ol ( 2E indicates that in the C=C at C-2, the senior alkyl groups lie on the opposite side) (Note that R,S notations belong to optical isomerism and E, Z notation belong to geometrical isomerism. These two isomerism belong to stereoisomerism. You will know the details of isomerism from other books. Here the basis of writing full correct name is given. The beginners will definitely face difficulty in naming such stereoisomeric structures until they study the chapter stereoisomerism. So you are advised not to bother about E/Z and R/S now until you study that) 27. 2-(pentyloxy)ethanol 28. 1-(prop-1-enyloxy)acetone 29. 1-(but-2-enyl)cyclohexene (note that in Q. 28 and 29, the stereochemical notation E has been dropped) 30.isoprene(PIN)/2-methylbuta-1,3-diene 31. styrene(PIN)/vinylbenzene 32. 1,6-dimethylcyclohexene(not 2,3-dimethylcyclohexene as it violates the lowest set of locants rule) 33. dimethyl phthalate 34. 2-ethylcyclobutanecarbonitrile 35. 6-mercaptocyclohex-4-ene-1,3-diol (lowest set of locants for -ol followed by lower locant to - ene gives the correct name) 36. 3-(ethylthio)hexane 37. 1,3,5-tribromo-2-chlorobenzene 38. 2-bromo-5-hydroxy-3-nitrobenzoic acid 39. 2-(3-methylbutyl)cyclopentanol 40. N-methylhex-5-en-1-amine(PIN)/N-hex-5-enyl-N- 41. 3-methylpyrrole 42. 2-methylpyridine 43. 2-[2-(ethoxymethoxy)ethoxy]butane 44. 1-ethyl-3-methoxybenzene 45. 1-but-1-enyl-4-methylbenzene/ 1-[(1Z)-but-1-enyl]-4-methylbenzene Nomenclature of Organic Compounds

REFERENCES

1. Nomenclature of Organic Chemistry (1979 Edition) J.Rigauidy and S.P.Klesney, Pergamon Press, OXFORD 2. A guide to IUPAC nomenclature of Organic Compounds (1994 edtion) R. Panico, W. H. Powell and Jean-Claude Richer, Blackwell Scientific Publications, OXFORD 3. IUPAC Recommendations(2002); www.iupac.org 4. On-line IUPAC Naming : www.iupac.org/nomenclature 5. Schaum’s 3000 Solved Problems in Chemistry, D. E. Goldberg, McGraw Hill Book Companty(New York) Concepts in Chemistry Chapter-IV ISOMERISM Organic compounds have a unique charateristics of exhibiting isomerism. We have mentioned this in the chapter "chemical bond" under covalent bonding. Organic molecules contain covalent bonds between the various atoms and can be arranged in various different ways to give different compounds having same formula. are different compounds having different properties but having same . The phenomenon is called isomerism. There are two types of isomerism namey structural isomerism and stereoisomerism. We shall only discuss structural isomerism now and in higher classes we shall study stereoisomerism. In structural isomerism, the structures of the isomers are different. Look to the following example.

Molecular Formula: C4H10

This is an alkane, as it is in agreement with the formula CnH2n+2 where n=4. We can have two alkanes possible from this formula.

H3C CH CH3 H3CCH2 CH2 CH3 (butane) (2-methylpropane or isobutane) H3C

The two compounds have the same formula(C4H10), but their structures are different, their names are different. Their properties are different for example, their boiling points are different. These are called structural isomers. Commonly when we say isomerism, we mean the structural isomerism. Let us study more about structural isomerism in a systematic way. 1. Isomerism in Alkanes:

(i)The formula CH4, C2H6 and C3H8 have no isomers. But from C4H10 onwards, isomerism is exhibited. We have already discussed isomerism in C4H10.

(ii)Isomerism in C5H12: Try to write as many structures as possible from the formula

C5H12. Name each by IUPAC system.

H3CCH2 CH2 CH2 CH3 (pentane or n-pentane)

H3CCHCH2 CH3 (2-methylbutane or isopentane) CH3

CH3 H CCCH 3 3 (2,2-dimethylpropane or neopentane) CH3 Try for more. You will not find any other isomer than the above three. You can know this when you wirte the IUPAC name of a suspected new isomer. It will be merely repetition of the previous isomers. Thus the formula C5H12 can have three isomers.

2. Isomerism in Alkenes(CnH2n)

The formula C2H4, C3H6 do not exhibit isomerism. Isomerism starts from the formula

C4H8. Nomenclature of Organic Compounds

Isomerism in C4H8: There are three isomers possible from this formula.

H2CCHCH2 CH3 (but-1-ene), H3CCHCHCH3 (but-2-ene)

H3C C CH2 (2-methylpropene or isobutene) H3C Can you get any other structural isomer from this formula? Try. You will not find any more.

3. Isomerism in Alkyne(CnH2n-2 ):

C2H2, C3H4 do not show isomerism. However from C4H6 onwards, we find more than one isomers from each formula.

Isomerism in C4H6: You know that contain one triple bond. Only two isomers are possible.

HC C CH2 CH3 (but-1-yne) H3CC C CH3 (but-2- yne) 4. Isomerism in Haloalkanes: Mono haloalkanes(haloalkane containing one atom) containing more than three carbon atoms show isomerism. Look to this example.

Formula: C3H7Cl: We have two isomers possible from this formula.

H3CCH2 CH2 Cl (1-chloropropane)

Cl (2-chloropropane) H3CCHCH3

5. Isomerism in Alcohols/Ethers(CnH2n+2O)

The formula for both alcohol and ether is CnH2n+2O. See this example.

(i) Isomerism in C2H6O:

We can get only one alcohol from this formula i.e CH3-CH2-OH(ethyl alcohol). We can

get one ether from the same formula i.e CH3-O-CH3(methoxy methane or ). So alcohol and ethers are isomers.

(ii) Isomerism from the formula C3H8O: Alchohols: We can have two alcohols from this formula.

H3CCH2 CH2 OH (propan-1-ol or n-propyl alchohol)

OH ( propan-2-ol or isopropyl alcohol) H3C CH CH3 Ethers: We can have only one ether possible from this formula.

H3CCH2 OCH3 ( or ethyl methyl ether) Concepts in Chemistry

6. Isomerism in Aldehydes/Ketones(CnH2nO):

The formula for both aldehyde and ketone is CnH2nO. These are isomers. See this example.

(i) Isomerism in C3H6O: We can get one aldehyde and one ketone from this fomula.

O O (propanal) (propanone or H3CCH2 C H H3CC CH3 acetone)

(ii) Isomerism from the formula C4H8O: Aldehydes: Two aldehdydes are possible from the formula.

O (butanal), H3CCH2 CH2 C H

CH3 O (2-methylpropanal) H3CCH C H Ketone: Only one ketone is possible from this formula.

O (butan-2-one or ethyl methyl ketone) H3CCCH2 CH3 Are you thinking of another ketone , butan-3-one(!!!). There is nothing called butan-3- one. This name is wrong. The locant of -one(ketone) should be minmum. Reverse the numbering and you will find it to be butan-2-one.

7. Isomerism in Carboxylic Acids and Esters(CnH2nO2 ):

Carboxylic acids and esters have the same formula CnH2nO2 and they are isomers.

(i) Isomers from the formula C3H6O2: Carboxylic acid: Only one carboxylic acid is possible.

O (propanoic acid). H3CCH2 C OH Esters: Two esters are possible from this formula.

O (methyl ethanoate or ) H3CCOCH3

O (ethyl methanoate or ) HCOCH2 CH3

Thus we found here that the formula C3H6O2 gave rise to three isomers, one among them is a carboxylic acid and the other two are esters. Nomenclature of Organic Compounds SAQ 1: Write down the structures and names(IUPAC) of all the isomers possible from the the following formula.

(1)C6H14 (2)C4H10O (3)C5H8

CLASSIFICATION OF STRUCTURAL ISOMERISM: There are many types of structural isomerism out of which we have already discussed the following three types. (a) Chain Isomerism: The isomers differ in the nature of carbon skeleton(word root). Examples: (i)Butane and 2-methylpropane (ii) pentane and neopentane etc. (b) Position Isomerism: The isomers differ in the position of functional group or braches while the carbon skeleton remaining the same. The word root remain the same. Examples: (i) But-1-ene and but-2-ene (ii) propan-1-ol and propan-2-ol (iii) pentan-2-one and pentan-3-one (c) Functional Isomerism: The isomers differ in the nature of the functional groups. Examples: (i) Ethanol and methoxymethane (alcohol and ether) (ii) propanone and propanal (aldehyde and ketone) (iii) ethanoic acid and methyl methanoate (carboxylic acid and ester)

Other structural isomerisms such as tautomerism, metamerism and ring-chain isomerism have not been discussed here.

RESPONSE TO SAQ SAQ 1:

H3CCH2 CH2 CH2 CH2 CH3 (hexane or n-hexane)

H3CCHCH2 CH2 CH3 ( 2-methylpentane or isohexane) CH3

H3CCH2 CH CH2 CH3 (3-methylpentane) CH3

CH3 H CCCH CH 3 2 3 (2,2-dimethylbutane or neohexane) CH3 Concepts in Chemistry

CH3 CH3

H3CCHCHCH3 (2,3 dimethylbutane

2. The formula C4H10O is in agreement with the general formula, CnH2n+2O. This belongs to the category alcohol/ether. Alcohol: Four alcohols are possible from this formula. You can try for more, but you shall fail.

(i) H3CCH2 CH2 CH2 OH (butan-1-ol or n-butyl alcohol)

OH (ii) (butan-2-ol or sec. butyl alcohol) H3CCH2 CH CH3

CH3 (iii) (2-methylpropan-1-ol or isobutyl alcohol) H3CCHCH2 OH

OH

(iv) H3CC CH3 ( 2-methylpropan-2-ol or tert. butyl alcohol) CH3 Ether: There are three ethers possilbe from the formula.

(i) H3CCH2 OCH2 CH3 (ethoxyethane or diethyl ether)

(ii) H3COCH2 CH2 CH3 (1-methoxypropane or methyl n-propyl ether)

CH3 (iii) H3COCH (2-methoxypropane or methyl isopropyl ether) CH3

3. C5H8 agrees to the formula CnH2n-2. It is an alkyne. Three isomers are possible.

(i) HC C CH2 CH2 CH3 (pent-1-yne) (ii) CH3 CCCH2 CH3 (pent-2- yne)

CH3 (iii) HC C CH (3-methylbut-1-yne) CH3 Other isomers containing two double bonds are also possible which we shall not take now.