IUPAC Rules for Nomenclature

IUPAC Rules for Nomenclature - IUPAC Rules for Naming...

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IUPAC Rules for Naming Organic Molecules From J. Chem. Ed. Article by Stanislaw Skonieczny To name a compound using the IUPAC system, follow the steps shown (if applicable) in the following order. Step 1 Determine the principle functional group in the compound. When a compound contains more than one group in Table 1, the principle group is that which has the highest precedence. This group will be cited as a suffix; all other groups are cited as prefixes. a (C) designates a carbon atom included in the parent hydrocarbon (part of the longest chain or ring. * and ** These are always used as a suffix. If a higher priority group is present in the molecule the suffix is changed to –en– or –yn– and is followed by the suffix of the higher priority group. Functional Group Suffix if Highest Precedence Prefix if Lower Prededence -(C) a OOH -oic acid - -COOH -carboxylic acid carboxy- -SO 2 OH -sulfonic acid sulfo- -C(O)OC(O)- -oic anhydride - -(C)OOR alkyl -oate alkoxy-oxo- -COOR alkyl carboxylate - -(C)OX -oyl halide halo-oxo- -COX -carbonyl halide halocarbonyl- -(C)ONH 2 -amide amino-oxo- -CONH 2 -carboxamide aminocarbonyl- -(C)≡N -nitrile - -C≡N -carbonitrile cyano- -(C)HO -al oxo- -CHO -carbaldehyde formyl- >(C)=O -one oxo- -OH -ol hydroxy- -SH -thiol sulfanyl- -NH 2 -azane (-amine) azanyl- (-amino) >NH -azane (-imine) azanylidene- >C=C< -ene * -C≡C- -yne ** -X, -R, -OR - halo-, alky-l, alkoxy- -Ar, -NO 2 - aryl-, nitro- -NO, -N 3 - nitroso-, azido- =N 2 , -SR - diazo-, ( R )-sulfanyl-
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OH O H OH Step 2 Determine the parent hydrocarbon (principle chain or ring system system): (a) If the principle group occurs in a chain, the principle chain is selected as (i) the chain containing the functional group of the highest seniority as the parent. 2-(propan-1-yl)pentan-1-ol (ii) If more than one such choice is possible, select the chain with the maximum number of multiple bonds. 2-(hexan-1-yl)buta-1,3-diene (iii) If (i) and (ii) together are not definitive, then choose the longest chain. (iv) If two chains of the same length are possible, choose the one with the maximum number of substituent groups. 2-(butan-1-yl)-4-methylhexanal The parent chain here contains six carbon atoms. (b) If the principle functional group occurs in a cyclic system, that system forms the parent. 2-(octan-1-yl)cyclohexanol 2-(hexan-1-yl)cyclopentene
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O 1 2 3 4 5 6 1 2 3 4 5 6 Step 3 Name the parent structure of and the principle group(s). Give the parent name the same name as if it were an alkane, but replace –ane with the suffix characteristic of the functional group of the highest priority (Table 1). Note: Multiple unsaturation in hydrocarbons is indicated by the numerical prefixes di- , tri- , etc. In such cases, however, the ending –ane of the parent alkane is replaced with –adiene , –atriene , etc. leaving the “ a ” in the root alkane name whenever the first letter of the suffix is a consonant to make the name easier to pronounce. Thus we get
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IUPAC Rules for Nomenclature - IUPAC Rules for Naming...

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