Homologous series are families of organic compounds with the same functional group and same general formula. •They show a gradual change in physical properties (e.g. boiling point). • Each member differs by CH2 from the last. • same chemical properties. Functional group is an atom or group of atoms which when present in different molecules causes them to have similar chemical properties homologous series functional group prefix / suffix (* = usual use) example Alkane -ane CH3CH2CH2CH3 Butane Alkenes suffix -ene Alcohols suffix* -ol prefix hydroxyHalogenoalkanes prefix chloro- bromoiodo- Aldehydes suffix -al prefix formylKetones suffix* -one prefix oxocarboxylic acids suffix -oic acid Esters -yl –oate C C C OH H H C H C H H C H H O H C halogen H C C H Cl H H H C H H C O H C C O H H H H C O C C O C H H H H H H C O OH C C O OH H H H C C O O H H H C H H H propene Propan-1-ol 1-chloropropane ethanal Propanone Ethanoic acid C methylethanoate O O C C C C H C H H H H H OH Cl O O OH O O O code no of carbons meth 1 eth 2 prop 3 but 4 pent 5 hex 6 hept 7 oct 8 non 9 dec 10 General rules for naming carbon chains Count the longest carbon chain and name appropriately Find any branched chains and count how many carbons they contain Add the appropriate prefix for each branch chain Eg -CH3 methyl or -C2H5 ethyl –C3H7 propyl 3,5-dimethylheptane Basic rules for naming functional groups N Goalby chemrevise.org 3 H3C CH CH2 CH2 CH3 CH CH2 CH3 CH3 1 2 3 4 5 6 7 The position of the functional group on the carbon chain is given by a number – counting from the end of the molecule that gives the functional group the lowest number. For aldehydes, carboxylic acids & nitriles, the functional group is always on carbon 1. Butan-1-ol We only include numbers, however, if they are needed to avoid ambiguity. H C C C H H H H H H C H H H methylpropane Words are separated by numbers with dashes numbers are separated by commas If there is more than one functional group or side chain, the groups are listed in alphabetical order (ignoring any di, tri). The suffix for alkenes can go in front of other suffixes. •When using a suffix, add in the following way : If the suffix starts with a vowel- remove the –e from the stem alkane name e.g. Propan-1-ol, butan-1-amine, ethanoic acid, ethanoylchloride, butanamide If the suffix starts with a consonant or there are two or more of a functional group meaning di, or tri needs to be used then do not remove the the –e from the stem alkane name e.g. Propanenitrile, ethane-1,2-diol, propanedioic acid, propane-1,2,3-triol, Pentane-2,4-dione. •The functional groups take precedence over branched chains in giving the lowest number 3-methylbut-1-ene is correct and not 2-methylbut-3-ene CH2FCH2CHBrCH2CH3 3-bromo-1-fluoropentane CH2FCCl2CH2CH3 2,2-dichloro-1-fluorobutane. 2,3-dibromopentane. CH 2-bromobut-3-en-1-ol 2OHCHBrCH=CH2 C C C C C Br H H H H H Br H H H H H CHCl3 trichloromethane Where there are two or more of the same groups, di-, tri- , tetra-, penta- or hexa- are used. Note the point made above about the addition of ‘e’ to the stem H C C C C H H H H H H H O H H 4 3 2 1 code no of carbons meth 1 eth 2 prop 3 but 4 pent 5 hex 6 hept 7 oct 8 non 9 dec 10 General rules for naming carbon chains Count the longest carbon chain and name appropriately Find any branched chains and count how many carbons they contain Add the appropriate prefix for each branch chain Eg -CH3 methyl or -C2H5 ethyl –C3H7 propyl 3,5-dimethylheptane Basic rules for naming functional groups The functional group is named by a prefix or suffix. e.g. bromoethane, ethanol, propene The position of the functional group on the carbon chain is given by a number – counting from the end of the molecule that gives the functional group the lowest number. We only include numbers, however, if they are needed to avoid ambiguity. H C C C H H H H H H C H H H methylpropane Where there are two or more of the same groups, di-, tri- , tetra-, penta-, hexa- are put before the suffix/prefix. CH2FCH2CHBrCH2CH3 3-bromo-1-fluoropentane CH2FCCl2CH2CH3 2,2-dichloro-1-fluorobutane. 2,3-dibromopentane. CHCl3 trichloromethane The suffix for alkenes can go in front of other suffixes. CH 2-bromobut-3-en-1-ol 2OHCHBrCH=CH2 4 C C C C C Br H H H H H Br H H H H H Words are separated by numbers with dashes. Numbers are separated by commas. If there is more than one functional group or side chain, the groups are listed in alphabetical order (ignoring any di, tri). Halogenoalkanes Class the halogen as a substituent on the C chain and use the suffix -fluoro, -chloro, -bromo, or –iodo. (Give the position number if necessary) 2-bromobutane Alcohols These have the ending -ol and if necessary the position number for the OH group is added between the name stem and the –ol If the compound has an –OH group in addition to other functional groups that need a suffix ending then the OH can be named with the prefix hydroxy-: CH3 CH CH2 CH3 OH 1 2 3 4 Butan-2-ol H3C CH C O OH OH 2-hydroxypropanoic acid HO CH2CH2 OH H C2 HC H C2 OH OH OH If there are two or more -OH groups then di, tri are used. Add the ‘e’ on to the stem name though. Ethane-1,2-diol propane-1,2,3-triol 5 N Goalby chemrevise.org H C C C C H H H H H Br H H H C O C H H H H Aldehydes An aldehyde’s name ends in –al It always has the C=O bond on the first carbon of the chain so it does not need an extra number. It is by default number one on the chain. Ethanal C C C O H H H H H H Propanone Ketones Ketones end in -one When ketones have 5C’s or more in a chain then it needs a number to show the position of the double bond. E.g. pentan-2-one Carboxylic acids These have the ending – oic acid but no number is necessary for the acid group as it must always be at the end of the chain. The numbering always starts from the carboxylic acid end. C C O O H H C H H H H Propanoic acid If there are carboxylic acid groups on both ends of the chain then it is called a – dioic acid C C O OH O HO Ethanedioic acid Note the e in this name C C C O H H H H C H C H O H H Pentane-2,4-dione If two ketone groups then di is put before –one and an an e is added to the stem. Esters Esters have two parts to their names C C C O O C H H H H H H H H The bit ending in –yl comes from the alcohol that has formed it and is next to the single bonded oxygen. The bit ending in –anoate comes from the carboxylic acid. (This is the chain including the C=O bond) methylpropanoate O O
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3.3.1.1 Nomenclature
The characteristics of a homologous series, a series of compounds containing the same functional group.
IUPAC rules for nomenclature.
Students should be able to:
• apply IUPAC rules for nomenclature to name organic compounds limited to chains and rings with up to six carbon atoms each
• apply IUPAC rules for nomenclature to draw the structure of an organic compound from the IUPAC name limited to chains and rings with up to six carbon atoms each.