B11CC3B17CA Naming Organic Chemicals B17CA Naming Organic Chemicals

Naming Alkenes

Alkenes are named in the same way that alkanes are named except that you use -ene as the stem ending.

A comprehensive set of nomenclature rules has been devised by the International Union of Pure and The parent chain for the name is the longest chain containing the alkene group. Applied Chemistry (IUPAC). This sheet explains basic chemical nomenclature. Use a locant to indicate the position of the alkene and number from the end of the chain that gives the lowest value to this locant. Naming Alkanes 5 8 Straight chain alkanes are named with a stem to indicate the number of carbons in the chain followed CH2CH2CH2CH3 by the ending -ane. 1 ALKANE CH3CH2CH2CHCH3 4-methyloctane 4 methane CH4 hexane CH3CH2CH2CH2CH2CH3 ethane CH3CH3 heptane CH3CH2CH2CH2CH2CH2CH3 5 3 2 8 propane CH CH CH octane CH CH CH CH CH CH CH CH 3 2 3 3 2 2 2 2 2 2 3 CH2CH CHCH3 butane CH3CH2CH2CH3 nonane CH3CH2CH2CH2CH2CH2CH2CH2CH3 8 pentane CH CH CH CH CH decane CH CH CH CH CH CH CH CH CH CH ALKENE CH3CH2CH2CHCH3 5-methyloct-2-ene 3 2 2 2 3 3 2 2 2 2 2 2 2 2 3 5 For branched alkanes choose the longest chain as the parent chain for the name and include the side locant indicates position of double bond chains as prefixes: methyl-, ethyl-, propyl-, butyl- etc. stem ending -ene 5 8 Notice that the locant indicating the position of the double bond is located BEFORE the ending 1 CH2CH2CH2CH3 4-methyloctane ‘-ene’. So the name of the above alkene is 5-methyloct-2-ene. CH3CH2CH2CHCH3 4

Use numbers (locants) to indicate the position of the side chains. Always start numbering from the Naming Alkyl Halides end of the parent chain that will give the lowest locant to the substituent. So the example above is 4- methyloctane NOT 5-methyloctane. Alkyl halides are named using prefixes (fluoro-, chloro-, bromo-, iodo-) to indicate the presence of halogen atoms. Use locants as usual to designate the position of the halogen atom in the . For multibranched alkanes introduce all the side chains as prefixes in alphabetical order. When As before, number the main carbon chain from the end that gives the lowest locant numbers to the more than one of the same substituent is present use multipliers (di-, tri- tetra- etc) to indicate the attached groups! number of these present: Br 9 hyphens to separate locants from name CH3CHCH2CH2CH3 2-bromopentane not 4-bromopentane CH3CH2 CH2CH2CH2CH3 3-ethyl-2,5-dimethyl-5-propylnonane CH3CHCHCH2CCH3 1 CH3 CH CH CH CH 3 2 2 3 m p alphabetical order e CH3CH2CH2CCH3 2-chloro-2-methylpentane not 4-chloro-4-methylpentane NO spaces between locants & hyphens NO spaces between locants & names Cl NO spaces between locants & commas Br Br

CH3CH2CH2CH2CH2CHCH2 1,2-dibromoheptane not 6,7-dibromoheptane

Principles of Chemistry • B17CA! 1 Principles of Chemistry • B17CA! 2 B17CA Naming Organic Chemicals B17CA Naming Organic Chemicals

O Naming Alcohols CH CH CH CCH pentan-2-one 3 2 2 3 require a locant to indicate where the C=O Alcohols are named using a suffix -ol to indicate the presence of the . Choose the O group is located in the chain. Place the locant BEFORE longest chain containing the functional group and number the chain from the end that gives the low- the -one. CH3CH2CCH2CH3 pentan-3-one est locant to the carbon attached to the OH group.

CH3CH2OH ethanol Suffix -ol added to hydrocarbon chain indicates alcohol group. Other go into the name as prefixes. It’s the position of the or group that controls which end of the chain you number from. Remove e from stem ending -ane because suffix begins with vowel. So name is ethanol NOT ethaneol Cl O O OH OH CH3CHCH2CCH3 4-chloropentan-2-one CH3CH2CHCCH3 3-methylpentan-2-one CH CH CH CH CHCH 3 2 2 propan-1-ol 3 3 propan-2-ol CH3 Locant indicates position of OH group. Locant should be BEFORE the ending -ol. O OH CH3CH2CHCH2CH 3-bromopentanal 2-methylpropan-2-ol Substituents are named as normal with prefixes e.g. 2-methyl CH3CCH3 Br CH3

Naming Alkenes Containing Functional Groups CH3 OH OH When 2 alcohol groups are present the compound is named as a -diol like this. CH3CHCH2CHCHCH3 5-methylhexane-2,3-diol When no alcohol, aldehyde or ketone is present, it’s the position of the alkene that controls which end of the chain you number from:

Naming and Ketones position-1

Ketones and aldehydes are that contain a C=O group. They are named respectively using CH3 -one and -al suffixes. Note that an aldehyde group is always at the end of a carbon chain so no locant CH2=CHCH2CCH3 4-chloro-4-methylpent-1-ene is necessary because it will always be in position-1. Ketones require a locant to indicate where the Cl C=O group is located in the carbon chain. When an alcohol, aldehyde or ketone is present, it’s the position of the functional group NOT the al- O O kene that controls which end of the chain you number from: R C R R C H indicates position of alcohol functional group KETONE ALDEHYDE CH3 Note you will often see the aldehyde functional group CH =CHCH CCH 2-methylpent-4-en-2-ol O written as CHO without explicitly showing the C=O; 2 2 3 pentanal would be written: CH CH CH CH CHO OH CH3CH2CH2CH2CH pentanal 3 2 2 2 position-4 indicates position of double bond

No locant necessary for the aldehyde group as it's In the above example the name is based on pentene (the longest carbon chain). Take off the end ‘e’ ALWAYS at the end of the chain. Notice that the name is and add ‘-2-ol’ for the alcohol (numbering from the end of the chain that gives the lowest number for based on pentane for a chain of 5 carbons; this includes the the OH position): penten-2-ol. Add the number ‘-4-’ to indicate the location of the alkene double bond: carbon which is part of the aldehyde functional group. pent-4-en-2-ol. Finally add in the extra methyl branch at the front of the name: 2-methylpent-4-en-2-ol.

Principles of Chemistry • B17CA! 3 Principles of Chemistry • B17CA! 4