When naming compounds, where are you meant to put the number of the functional group?
Because some of the compound names I have seen have them at the start and others in the middle? Is there a reason for this?
Kia ora!
The number is put immediately before the part of the name to which they relate – such as the functional group
e.g., hex-2-ene has an alkene functional group, and the double bond starts on the second carbon (is between the second and third carbons).
Note: before 1993 (when the IUPAC rules were changed) the naming would have been 2-hexene – but this naming is now obsolete.
If the compound had a methyl group attached, then the number showing where the methyl group is attached would be in front of methyl
e.g., 3-methylhex-2-ene
The double bond is between the second and third carbons so the number 2 is placed before the “ene”; the compound also has a methyl side chain attached to the third carbon atom so the number 3 is placed before the “methyl”.
Good luck!
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Good answer Ben. But it is quite possible that some of the older (but still in common usage forms) will be accepted by markers. e.g 1-butanol could be accepted as an alternative to the correct butan-1-ol.
As an aside, for simple molecules where a number is not necessary as there is no possible confusion using ethan-1-ol instead of the correct ethanol form could be penalised. However, writing something like 2-methylpropane (where the 2 is redundant as the second carbon is the only place the methyl group could be attached to) instead of methylpropane should be accepted as it is not so obvious to see that it is not necessary.