OCR Chemistry 2.1.1 Nomenclature - naming of organic compounds

Naming of organic compounds involves following these steps:

1) count the number of carbon atoms in the longest unbranched chain to give the main root of the name:

• 1 Carbon = meth
• 2 Carbons = eth
• 3 = prop
• 4 = but
• 5 = pent
• 6 = hex
• 7 = hept
• 8 = oct
• 9 = non
• 10 = dec

2) if the atoms are arranged in a ring then put cyclo before root name e.g. cyclohex

3) if it is saturated (single C-C bonds only) -an- comes after root name

if it is unsaturated (double C=C bond/s) -en- comes after root name

4) for functional groups a prefix/suffix is used (you only need to know these ones). R represents a variable group:

• alkane -ane or -yl C-C
• alkene -ene C=C
• halogenoalkane fluoro-/chloro-/bromo- R-Hal
• alcohol -ol or hydroxy- R-O-H
• ketone -one R-C-R (O double bonded to C in ketone, aldehyde, carboxylic acid and ester but unable to show this using a keyboard)
• aldehyde -al R-C-H
• carboxylic acid -oic acid R-C-OH
• ester -oate R-C-O-R

5) if no functional group present, add e onto the end of the name

6) if the carbon chain is branched (meaning there are further side carbon chains attached to the longest carbon chain), then count how many carbons in the side carbon chain:

• 1 carbon = methyl
• 2 = ethyl
• 3 = propyl
• 4 = butyl

7) a number is used to indicate the position of a side chain or functional group. Number the carbon atoms from either side of the chain, making sure that the functional group/side chain is on the lowest numbered carbon atom

8) if there is a double bond then a number before the -en- indicates this

9) aldehydes, carboxylic acids and nitriles are always regarded as containing carbon number 1 in the chain

10) if there is the same functional group more than once add a prefix:

• twice di-
• three times tri-
• four times tetra-

11) positions and manes of functional groups must be in alphabetical order

12) if there are 2 or more functional groups this usually requires suffixes to be used. The ending for a carboxylic acid takes priority over an aldehyde or ketone. Then alcohol has the lowest priority