Common Prefixes and Suffixes in Organic Chemistry Nomenclature Hydrocarbon name: These are determined by the longest carbon chain length that contains the functional group described by the suffix. You number the carbons such that the suffix functional group has the lowest possible number. For some prefixes, you use the base name of the hydrocarbon chain, which is just the hydrocarbon name without the –ane ending (e.g. meth-; eth-; prop-) Name number of carbons Name number of carbons methane 1 undecane 11 ethane 2 dodecane 12 propane 3 tridecane 13 butane 4 tetradecane 14 pentane 5 pentadecane 15 hexane 6 hexadecane 16 heptane 7 heptadecane 17 octane 8 octadecane 18 nonane 9 nonadecane 19 decane 10 eicosane 20 Suffixes: These are ranked in order of precedence, so use the highest functional group on the list as the suffix. If the functional group appear more than once in a molecule, then include the number modifier (di-, tri- etc.) in the suffix (e.g. a double alcohol is a -diol, three double bonds is a -triene). If you are using a number modifier, then you use the whole alkane name and then add the number modifier and the suffix (1,3-propanediol). The suffix can be a compound suffix if an alkene/alkyne is involved, in which case you give the location number of each functional group in the suffix (e.g. HO-CH2-CH=CH-CH3 is but-2-en-1-ol) Functional group Formula Suffix Example carboxylic acid −C(O)−OH -oic acid propanoic acid anhydrides R−C(O)−O−C(O)−R’ (acid name) anhydride propanoic acid anhydride ester −C(O)−O−R -oate ethyl propanoate acid halides −C(O)−X 1 -oyl halide propanoyl chloride amide −C(O)−NH− -amide propanamide nitrile −C≡N (whole alkane name)-nitrile propanenitrile aldehyde −C(O)H -al propanal ketone −C(O)− -one 2-propanone alcohol −OH -ol 1-propanol thiol −SH (whole alkane name)-thiol 1-propanethiol amine R−NH2 or R−NH−R or (R)3N 2 (R)-amine2 1-propylamine ether C−O−C ether methyl propyl ether sulfides C−S−C sulfide methyl propyl sulfide disulfides C−S−S−C disulfide methyl propyl disulfide alkenes −CH=CH− -ene3,4 1-propene (prop-1-ene)3,4 alkynes −C≡C− -yne3,4 1-propyne (prop-1-yne)3,4 alkanes −CH2CH2CH2− -ane propane 1 X = a halogen (chloride, bromide, etc.) 2 R = the alkyl attachments to the amine (e.g. propylamine). If there are more than one alkyl groups attached to the amine, then the shorter alkyl groups are denotes as N-alkyl prefixes. (e.g. N-methyl propylamine) 3 In 1993, IUPAC switched to include the carbon number in the suffix of alkenes and alkynes. For example CH3-C≡C-CH3 is but-2-yne. This helps clarify the location of the double or triple bond in complex molecules that have other functional groups that take precedence. 4 For multiple double/triple bonds, you use the base hydrocarbon name (buta-, penta-, hexa-, etc.) followed by the number modifier (di, tri, etc.) and then the –ene or yne ending (e.g. buta-1,3-diene).Prefixes: Some of these functional groups can be suffixes as well. Use them as prefixes only if another functional group with a higher priority is already used as the suffix. Type of functional group Formula Name hydrocarbon −CH3 methyl- −CH2CH3 ethyl- −CH2CH2CH3 n-propyl- −CH2CH2CH2CH3 n-butyl- −C6H5 (aromatic ring) phenyl- −CH2−C6H5 (aromatic ring) benzyl- halogen −F fluoro- −Cl chloro- −Br bromo- −I iodo- nitrogen containing group −NO2 nitro- −NO nitroso- −NH2 amino- −C≡N cyano- −N=N− azo- oxygen containing groups −OH hydroxy- −C(O)−CH3 acetyl- −C(O)− oxo- −O−R 1 (R)-oxy- 1 −C(O)−OH carboxy- sulfur containing groups −SH mercapto- −S−R 1 (R)-sulfanyl- 1 1 R = the base name of a hydrocarbon group (e.g. meth-, eth-, prop- etc.). For example -O-CH3 is methoxy- and –O-CH2CH3 is ethoxy. Number Modifiers: If there are more than one of a particular function group, then you add the number modifier to describe how many of the functional groups are present. (e.g. CCl3−CH3 is 1,1,1-trichloroethane). Note that number modifiers are sometimes used in suffixes as well (e.g. HOCH2CH2CH2OH = 1,3-propanediol). number prefix number prefix 1 mono- 6 hexa- 2 di- 7 hepta- 3 tri- 8 octa- 4 tetra- 9 nona- 5 penta- 10 deca- Miscellaneous notation: cis- = same side of a double bond trans- = opposite side of a double bond para- = obsolete term for 1,4- substitution on an aromatic ring, but it is still frequently used. meta- = obsolete term for 1,3- substitution on an aromatic ring, but it is still frequently used. ortho- = obsolete term for 1,2- substitution on an aromatic ring, but it is still frequently used. cyclo- = a cyclic non-aromatic hydrocarbon ring (e.g. cyclohexane) N- = a alkyl attachment to an amine n- = straight-chain alkanes without branches or substituents (termed “normal” alkanes). iso- = obsolete terminology for branched alkane (e.g. isooctane), but it is still commonly used.Common Names of Aromatic Compounds: The following are commonly-used common names that are used as the base name for some substituted aromatic hydrocarbons. Aromatic base name Substitutions Formula toluene methyl C6H5-CH3 xylene dimethyl (multiple isomers possible) CH3-C6H4-CH3 aniline amine C6H5-NH2 phenol1 hydroxy C6H5-OH benzaldehyde aldehyde C6H5-C(O)H benzoic acid carboxylic acid C6H5-COOH pyridine2 nitrogen heterocyclic C5H5N 1 phenol is a very weak acid with a pKa of 9.99. 2 pyridine is a base with a pKb of