Organic Chemistry Alkanes and Alkenes

Pure Hydrocarbons Because the main use of hydrocarbons is as a fuel there is no point in going to the effort to separate them into individual hydrocarbons. It is, however, possible to obtain pure hydrocarbons by very careful distillation. This section is about pure hydrocarbons.

Carbon: Organic Chemistry C

Alkanes The simplest hydrocarbons form a series of compounds known as alkanes. These all consist of carbon and hydrogen only and every carbon has four single covalent bonds. HydrocarbonFormulaStructure MethaneCH 4 EthaneC2H6C2H6 PropaneC3H8C3H8 ButaneC 4 H 10 hydrogen carbon

Names of Alkanes The names of the 4 simplest alkanes are methane, ethane, propane and butane. After that the names are systematic (like the words used to describe geometric shapes.) E.g. –5 carbons = pentane C 5 H 12 –6 carbons = hexaneC 6 H 14 –7 carbons = heptaneC 7 H 16 –8 carbons = octaneC 8 H 18 –9 carbons = nonaneC 9 H 20 –10 carbons = decaneC 10 H 22 carbon hydrogen pentane

Homologous Series Alkanes all have very similar structures. They have a CH 3 at each end of the molecule. What differs is the number of CH 2 groups between the two ends. These all consist of carbon and hydrogen only and every carbon has four single covalent bonds. It is possible to build up a series by simply adding an extra CH 2 group This leads to a general formula of C n H 2n+2 hydrogen carbon n= 1 n=2 n=3 n=4

What will be the formula for alkanes containing the following numbers of carbons? C 12 H 26 C 16 H 34 C 31 H 64 C 19 H 40 Activity Number of carbonsFormula

Formulae and Models of Alkanes methane, CH 4 C H H H H

C H H H H C H H H C H H H ethane, C 2 H 6 C H H H C H H C H H H propane, C 3 H 8 Alkanes

butane, C 4 H 10 C H H H C H H C H H C H H H pentane, C 5 H 12 C H H H C H H C H H C H H C H H H

C H H H C H H C H H C H H C H H C H H H hexane, C 6 H 14 and so on………… Notice the carbon chain is not really straight

Isomerism isomers. Alkanes of the same formula can have different arrangements of atoms. Such different arrangments are known as isomers. Two isomers of C 4 H 10 are shown Isomers of butane

Isomerism Naming: Find the longest chain this is called the backbone Isomers of butane

Isomerism Naming: Number the carbons Isomers of butane

Isomerism Isomers of butane N-butane 2-methylpropane

This is butane, but we call it n-butane n stands for normal

The longest chain is 3 carbons, so "propane". There is one carbon left. We call this "methyl". Therefore, methyl propane

n-pentane Methyl butane

Longest chain is 3, so propane 2 separate, one carbon side chains is dimethyl dimethyl propane

methyl pentane

Naming and Functional groups 2-ethyl -3-methyl-butane

Naming and Functional groups Locate the longest carbon chain Number the carbons from the end closest to the functional group (include the carbon that is part of the functional group

Naming alcohols Alcohols have the hydroxyl group -OH The prefix is the number of carbons in the longest chain Name the alkane and drop the letter e The suffix is -ol

If there are more than 2 carbons in the chain, use a number to indicate which carbon the –OH group is attached to (Number from the direction that gives the smallest number). The suffix is -ol

Naming ethers Ethers have an Oxygen in the chain of carbons Name the alkyl groups on either side of the O that is in the chain Shorter chain is named first If both alkyl groups are the same it is named once with the prefix DI in front of it

Naming aldehydes Aldehydes have a double bonded Oxygen on the last carbon in the chain Name the alkane, drop the e Suffix is –al

Naming ketones Ketones have a double bonded Oxygen on a carbon in the middle of the chain ( Not the last carbon ) Name the alkane; Drop the e; Suffix is -one If there are more than 4 carbons in the chain, use a number to indicate the location of the =O

Naming Haloalkanes Haloalkanes have a halogen attached Fluorine, Chlorine …. To name these remove the “ine” and replace with an “O”. Then use as a prefix

Draw the structure of CH 3 CH 2 CHBrCH 3 Count the number of bonds each carbon has CH 3 CH 2 CHBrCH Since each carbon must have 4 bonds the missing bonds are carbon to carbon bonds

CH 3 CH 2 CHBr CH c-c 2 c-c 2 c-c 1 c c

Draw the structure of CH 2 CHCH 3 June 6 th 2013

Naming carboxylic acids acids Acids have a carbonyl group and an OH They are essenially like an Aldehyde and an Alcohol added into the same molecule. Name the alkyl Chain and the swap the “e” for oic acid

42 Carboxylic Acids, Esters, Amines and Amides Carboxylic Acids Properties of Carboxylic Acids Esters Esterification and Hydrolysis

43 Carboxyl Group Carboxylic acids contain the carboxyl group on carbon 1. O  CH 3 — C—OH= CH 3 —COOH carboxyl group

44 Naming Carboxylic Acids Formula IUPAC Common alkan -oic acid prefix – ic acid HCOOH methanoic acid formic acid CH 3 COOH ethanoic acid acetic acid CH 3 CH 2 COOH propanoic acid propionic acid CH 3 CH 2 CH 2 COOH butanoic acid butyric acid

45 Naming Rules Identify longest chain (IUPAC) Number carboxyl carbon as 1 (Common) Assign , ,  to carbon atoms adjacent to carboxyl carbon CH 3 | CH 3 — CH—CH 2 —COOH IUPAC 3-methylbutanoic acid Common  -methylbutryic acid

46 Learning Check CA1 Give IUPAC and common names: A. CH 3 COOH CH 3 | B. CH 3 CHCOOH

47 Solution CA 1 A. CH 3 COOH ethanoic acid; acetic acid CH 3 | B. CH 3 CHCOOH 2-methylpropanoic acid;  -methylpropionic acid

48 Properties Carboxylic acids are weak acids CH 3 COOH + H 2 O CH 3 COO – + H 3 O + Neutralized by a base CH 3 COOH + NaOH CH 3 COO – Na + + H 2 O

49 Esters In an ester, the H in the carboxyl group is replaced with an alkyl group O  CH 3 — C—O —CH 3 = CH 3 —COO —CH 3 ester group

50 Esters in Plants Esters give flowers and fruits their pleasant fragances and flavors.

51 Naming Esters Name the alkyl from the alcohol –O- Name the acid with the C=O with –ate acidalcohol O  methyl CH 3 — C—O —CH 3 Ethanoate methyl ethanoate (IUPAC) (acetate)methyl acetate (common)

52 Some Esters and Their Names Flavor/Odor HCOOCH 2 CH 3 Raspberries ethyl methanoate (IUPAC) Pineapples CH 3 CH 2 CH 2 COOCH 2 CH 3 ethyl butanoate (IUPAC)

53 Amines Organic compounds of nitrogen N Classified as primary, secondary, tertiary CH 3 CH 3  CH 3 —NH 2 CH 3 —NH CH 3 —N — CH 3 1° 2° 3°

54 Naming Amines IUPAC aminoalkane CH 3 CH 2 NH 2 CH 3 —NH —CH 3 aminoethane methylaminomethane NH 2 | CH 3 CHCH 3 2-aminopropane

55 Learning Check AM1 Give the common name and classify: A.CH 3 NHCH 2 CH 3 CH 3 | B.CH 3 CH 2 NCH 3

56 Solution AM1 A.CH 3 NHCH 2 CH 3 ethylmethylamine, 2° CH 3 | B.CH 3 CH 2 NCH 3 ethyldimethylamine, 3°