Chapter 2/p1 CHAPTER TWO: ORGANIC CHEMISTRY Organic chemistry is the chemistry of compounds containing carbon. It is associated with living matter found in plants and animals, for e.g. carbohydrates, fats, proteins, vitamins, hormones, enzymes, drugs, wool, silk and linen. Perfumes, dyes, flavours, soaps, detergents, plastics, petrol and oils are also associated with organic chemistry. Carbon is in group lV in the periodic table and can have a maximum of four bonds. HYDROCARBONS Hydrocarbons are compounds that contain only carbon and hydrogen.

Chapter 2/p2 ALKANES Have only single bonds. General formula: C n H 2n+2 The three simplest alkanes contain 1, 2 and 3 carbon atoms respectively and are called methane (CH 4 ), ethane (C 2 H 6 ) and propane (C 3 H 8 ). Others are butane (4C), pentane (5C), hexane (6C), heptane (7C), octane (8C), nonane (9C) and decane (10C).

Chapter 2/p3 ALKENES AND ALKYNES Alkenes have a double bond and is given by the formula: C n H 2n Alkynes have a triple bond and is given by the formula: An example of an alkene is propene. C n H 2n-2 An example of an alkyne is propyne.

Chapter 2/p4 AROMATIC COMPOUNDS benzene

Chapter 2/p5 ALCOHOLS Contain the functional group, - OH and are named by replacing the ending ‘e’ of the corresponding alkane with ‘ol’. CH 3 – OH CH 3 CH 2 – OH CH 3 CH(OH)CH 3 methanol ethanol 2-propanol THIOLS Sulfur analogues of alcohols and contain an – SH functional group in place of an – OH group. CH 3 – SH CH 3 CH(SH)CH 3 methanethiol 2-propanethiol PHENOLS The – OH group is attached to benzene.

Chapter 2/p6 ETHERS An ether is formed during the dehydration of an alcohol. CH 3 CH 2 – OH HO – CH 3 ethanol methanol CH 3 CH 2 – O – CH 3 methyl ethyl ether Ethyl ether known as ether – general anesthetic. ALDEHYDES Prepared by the oxidation of primary alcohols. Contain a C = O functional group. CH 3 CH 2 – OH → CH 3 CHO ethanol ethanal

Chapter 2/p7 KETONES Prepared by the oxidation of secondary alcohols. 2-propanol propanone CARBOXYLIC ACIDS Prepared by the oxidation of aldehydes. propanal propanoic acid

Chapter 2/p8 ESTERS Produced by the reaction of a carboxylic acid with an alcohol. propanoic acid methanol methyl propanoate AMINES Derived from ammonia, NH 3. Aliphatic and aromatic amines. methylamine methyl ethylamine benzylamine (aniline)

Chapter 2/p9 HETEROCYCLIC COMPOUNDS Ring compounds in which one or more of the carbon atoms are replaced by nitrogen, sulfur or oxygen. pyrrole pyridine pyrimidine purine

Chapter 2/p10 NAMING OF ORGANIC COMPOUNDS Rule 1:Choose the longest carbon chain to base the name upon. Rule 2:Number the carbons in this longest chain beginning at the end nearest the first branch point. Rule 3:Identify and number the branches. -CH 3 -CH 2 CH -CH 2 CH 2 CH 3 -CH 2 CH 2 CH 2 CH 3 -CH 2 CH 2 CH 2 CH 2 CH methyl ethyl propyl butyl pentyl

EXAMPLE Name the following molecule: SOLUTION The longest carbon chain is seven atoms long Therefore our name will be based upon heptane. Chapter 2/p11

We now number the chain to give the following By numbering in this manner the branches are on the lowest carbon numbers possible, i.e. C3 and C4. We thus have a methyl group on C3 and a methyl group on C4. We can now write the name as 3,4-dimethylheptane. WHEN NAMING ORGANIC COMPOUNDS USE HYPHENS TO SEPARATE NUMBERS AND LETTERS, AND COMMAS TO SEPARATE NUMBERS. Chapter 2/p12

The chain is numbered in the direction that gives the highest priority functional group the lowest possible number. EXAMPLE Name the following compound FUNCTIONAL GROUPS Chapter 2/p13

The parent hydrocarbon is five carbons long The suffix will be –oic acid; The substituents are 3-methyl and 4-chloro. Thus, we have 4-chloro-3-methylpentanoic acid. SOLUTION Chapter 2/p14

EXAMPLE Name the following compound SOLUTION The highest priority functional group is the aldehyde. Thus the parent chain is numbered: Therefore the name is 5-hydroxy-5-methylhexanal Chapter 2/p15

Compounds with the same molecular formula but with different bonding arrangements called structural or constitutional isomers. Consider the compound, butane (C 4 H 10 ): Can obtain two isomers for butane: butane 2-methylpropane For pentane, have three isomers: 2-methylbutane 2,2-dimethylpropane ISOMERS pentane Chapter 2/p16