Chemistry for Changing Times,

Chapter 9 Organic Chemistry

John Singer, Jackson Community College Organic Chemistry

Organic chemistry is defined as the chemistry of hydrocarbons and their derivatives. Of tens of millions of known chemical compounds, over 95% are compounds of carbon. The Unique Carbon Atom

Carbon is unique in that carbon atoms can bond to each other to form long chains and rings. NOTE: Carbon can only form 4 total bonds (bonds can be single bond to another C, single bond to another H or double or triple bond to another C) (see board) Hydrocarbons

Hydrocarbons are the simplest organic compounds. Contains only carbon and hydrogen. Alkanes

Alkanes are hydrocarbons that contain only single bonds. Because all carbon-to-carbon bonds are single bonds, alkanes are often called saturated hydrocarbons.

The simplest hydrocarbon is methane (CH4). Alkanes

The general formula of alkanes is CnH2n+2. Alkanes alkanes name = number prefix (# of C) + suffix -ane. pent = 5 (pentagon) hex = 6 (hexagon) oct = 8 (octopus) dec = 10 (decade) memorize alkane names for 1st 10 C Alkanes

Ball-and-stick and space- filling models can be used to represent organic compounds. Alkanes Condensed structural formulas condensed structural formulas, C-to-H bond lines are omitted

Butane: CH3CH2CH2CH3 See structural formula on board for the butane. (note 4 bonds per C) Bond Line (or skeletal structures, not in text) Every bend, there is a C with correct # H

Butane: HW 9.1 structural formula, condensed formulas, skeletal formulas (a)Draw the structural formula for(4 bonds to C) CH CH CH CH 3 2 2 3 End 1/22 F (b)Draw skeletal formula for above

(c) Give condensed & skeletal formula for: H H H H H H C C C C C H H H H H H Alkanes

The alkanes represent a homologous series that differs by the number of —CH2— groups. Members of a homologous series exhibit properties that vary in a regular and predictable manner. Alkanes

Isomerism: Isomers are compounds with the same molecular formula but different structural formulas. Alkanes: Example Isomerism: Given the following molecule, give structural isomers and name the isomers. Worked on doc camera.

CH3CH2CH2CH2CH2CH2CH2CH2CH3 HW 9.2 Alkanes Isomerism: Given the following molecule, give 2 structural isomers.

End 1/25 M 1. CH3CH2CH2CH2CH2CH3

2. CH3CH2CH2CH2CH2CH2CH2CH3 Naming Organic Molecules prefix root suffix prefix – substituents ( alkyl, halo, etc) suffix – ene, —yne, -ol, -al, -one, -oic acid root – longest continuous alkane chain (containing both alkene or alkyne carbons if present) HOW TO Name an Alkane Using the IUPAC System Step [1] Find the root (longest continuous) carbon chain (root = alkane). (want simplest substituent chain)

• It does not matter if the chain is straight or it bends. Naming Structures with Chains of Equal Length • If there are two chains of equal length, pick the chain with more substituents. • In the following example, two different chains in the same alkane have seven C atoms. • We circle the longest continuous chain as shown in the diagram on the left, since this results in the greater number of substituents. (choose more # & simpler substituents)

17 Numbering Alkanes with Substituents

Step [2] Number the atoms in the carbon chain to give the first substituent the lowest number. Numbering Substituents

When numbering a carbon chain results in the same numbers from either end of the chain, assign the lower number alphabetically to the first substituent. Alkanes Cyclic Hydrocarbons

Cyclic hydrocarbons are ring compounds. The simplest cyclic hydrocarbon is cyclopropane. Cyclic Hydrocarbons The names of cyclic hydrocarbons consist of the prefix cyclo- followed by the name of the alkane with the same number of carbon atoms. (note: 4 bonds per C) (cycloctane, cyclodecane,etc.)

skeletal formula Cyclic Hydrocarbons When naming cycloalkanes with things hanging off main cycloalkane – number positions (lowest # possible) HOW TO Name a Cycloalkane Using the IUPAC System Cycloalkanes are named by using similar rules, but the prefix cyclo- immediately precedes the name of the parent.

root

Step [1] Find the root cycloalkane.

24 Numbering Substituents in Cycloalkanes

Step [2] Name and number the substituents. No number is needed to indicate the location of a single substituent.

For rings with more than one substituent, begin numbering at one substituent and proceed around the ring to give the second substituent the lowest number.

25 Unsaturated Hydrocarbons (still 4 bonds per C) Alkenes are hydrocarbons with a carbon-to-carbon double bond. Their general formula is CnH2n. Their names consist of a prefix denoting the number of carbon atoms, followed by the suffix -ene.

Ethylene (common name) is the simplest alkene. (or ethene – IUPAC name) (same as alkane but change -ane to -ene) Unsaturated Hydrocarbons

Alkynes are hydrocarbons that contain a carbon-to- carbon triple bond. Their general formula is CnH2n–2. same as alkane but replace –ane by suffix -yne.

Ethyne (IUPAC name) (acetylene – common name) is the simplest alkyne. Look at the formulas: (each extra bond between C, 2 less H)

• Alkane CnH2n+2

• Alkene CnH2n (one double bond)

• Alkyne CnH2n–2 (one triple bond) HW 9.3: Naming Organic Molecules Name the following.

H

(a) CH3 C CH2CH3

CH3

(b) Alkanes

Certain alkenes (and some cyclic hydrocarbons) can exist as cis–trans isomers. Cis–trans isomerism is a form of geometric isomerism whereby isomers have the same molecular formula and same connectivity but differ in their spatial orientation. Aromatic Hydrocarbons: Benzene and Relatives Benzene is a unique organic compound in that it is a very stable six-carbon ring with alternating single and double bonds. Aromatic hydrocarbons contain a benzene ring or have properties similar to those of benzene. Aromatic Hydrocarbons: Benzene and Relatives (special stability) Aromatic Hydrocarbons: Benzene and Relatives (name just like cycloalkane but use benzene as root name) common name Chlorinated Hydrocarbons

When chlorine is substituted for one or more hydrogen atoms of a hydrocarbon, a chlorinated hydrocarbon is formed. Chlorinated hydrocarbons have many useful properties. (halogenated hydrocarbon – any halogen)

Dichloromethane is used as a solvent and paint remover.

Trichloromethane (chloroform) is also a solvent and at one time was used as an anesthetic. It is now considered hazardous. Chlorofluorocarbons

Carbon compounds with both chlorine and fluorine are known as chlorofluorocarbons (CFCs). (freon – refrigerant) Functional Groups

Functional groups are atoms or groups of atoms that are attached to, or part of, the hydrocarbon skeletons and give the compounds characteristic chemical and physical properties. Double and triple bonds, as well as halogen substituents, are examples of functional groups. Functional groups react the same, have the same physical properties and function the same regardless of the rest of the molecule. (R = any alkyl group) Functional Groups Alkyl Groups – substituent alkanes

Alkyl groups are derived from the alkanes.

Alkane – ane + yl Alcohols

Alcohols contain the hydroxyl (—OH) functional group.

Examples include the following:

Methanol CH3OH

Ethanol CH3CH2OH

1-Propanol CH3CH2CH2OH Methanol

Methanol, or methyl alcohol, is sometimes called wood alcohol. It is an important solvent, automotive fuel additive, and possible fuel replacement. Ethanol

Ethanol, or ethyl alcohol, is also known as grain alcohol. It is the alcohol of beer, wine, etc. It is also an additive to automotive fuel and is being considered as a gasoline replacement. (most gas has 10% ethanol) Toxicity of Alcohols

All alcohols are toxic. Methanol, for instance, is oxidized to formaldehyde by liver enzymes. Formaldehyde is a poison and can cause blindness or death.

Even ethanol is toxic. The effects of drinking ethanol are due to its toxicity. Inebriety, alcoholism, and fetal alcohol syndrome are all due to the toxicity of ethanol. Ethanol Multifunctional Alcohols

Some alcohols contain more than one hydroxyl group.

antifreeze Phenols

Phenols are aromatic compounds with the hydroxyl group attached to the aromatic ring. The presence of the aromatic ring alters the properties of the hydroxyl group. Phenols do not act as alcohols but as acids. Phenols are effective antiseptics. Ethers

Ethers are compounds with two alkyl groups bonded to the same oxygen.

General formula: ROR or ROR (alkyl alkyl ether)

CH3CH2OCH2CH3 is diethyl ether.

CH3OCH2CH3 is ethyl methyl ether. Aldehydes and Ketones

Aldehydes and ketones are two families of organic compounds that contain the carbonyl (C=O) functional group.

Naming: suffix – al suffix -one Aldehydes and Ketone

O O O C C C

H H CH3 H CH3 CH3 formaldehyde acetaldehyde acetone common name methanal 1-ethanal 2-propanone IUPAC name HW 9.4: Name the Functional Group

H O O

(a) CH3 C CH2CH3 (c) CH3 C H

CH3

(b) (d) CH3 CH2 O H

End 2/1/21 Monday Carboxylic Acids

Organic acids contain the carboxyl (COOH) functional group.

IUPAC Naming – alkanoic acid Carboxylic Acids

When a carboxyl group is attached directly to a benzene ring, the compound is called benzoic acid. Reaction Carboxylic acid & alcohol → Ester

Esters are formed by replacing the hydrogen of a carboxylic acid with the alkyl group of an alcohol or phenol. Esters

Esters generally have a pleasant odor. Esters

Esters are named by stating the name of the alcohol part first, followed by the root name of the acid. Drop the -e and add the suffix -oate.

Example: Methyl butanoate Amines and Amides

Amines are derivatives of ammonia. When one or more hydrogens of ammonia are replaced by an alkyl group, an amine is the result. Like ammonia, amines tend to be basic and have similar odors. Amines and Amides Amines and Amides

Amides have nitrogen bonded to a carbonyl carbon.

The amino acids of proteins are linked by amide linkages. HW 9.5 Molecules can Contain Several Functional Groups Fill in the blank with the letter of the functional group. (A)alkene (B) alkyne (C) alcohol (D) ether (E) aldehyde (F) ketone (G) carboxylic acid (H) ester (I) amine (J) amide (will not use all, may use more than once)

58 Heterocyclic Compounds

Heterocyclic compounds are rings that contain atoms other than carbon as part of the ring. Most organic heterocyclic compounds contain nitrogen, oxygen, or sulfur. Alkaloids

Alkaloids are amines that occur naturally in plants, bacteria, fungi, and animals. Many have physiological effects. Morphine, caffeine, nicotine, and cocaine are alkaloids, and so are the bases pyrimidine and purine (DNA bases). Importance of Functional Groups

A functional group determines all of the following properties of a molecule: • bonding and shape • type and strength of intermolecular forces • physical properties • nomenclature • chemical reactivity

61 Reaction of alkene, alkynes - add H2 & X2 (alkyne can add 2 x)

H H H2 / Pd H H C=C H—C—C—H alkene H H H H

H H Br2 Br H C=C H—C—C—H alkene H H H Br

2 H2 H H H—C =C—H H—C—C—H alkyne H H

2 Br2 Br Br H—C =C—H H—C—C—H alkyne Br Br Alcohols Reactions Alcohols are oxidized to aldehydes & ketones [O] (if strong oxidation aldehydes oxidizes to carboxylic acid) O O

CH3OH → H C H → H O C O H O O

CH3CH2OH → CH3 C H → CH3 C OH

CH3CHCH3 → CH3 C CH3 OH O Reaction Carboxylic acid & alcohol → Ester

Esters are formed by replacing the hydrogen of a carboxylic acid with the alkyl group of an alcohol or phenol.