[Big-Daddy]

I have been given a list of general formulae for different organic functional groups, to which I've added a few. These are very helpful for me as they hugely narrow down the possibilities when I'm given a molecular formula (and usually some other info) and asked to identify the exact compound.

C_nH_2n+2 - Alkane
C_nH_2n - Alkene, cycloalkane
C_nH_2n-2 - Alkyne, 2 alkene C=C bonds, cycloalkane
C_nH_2n-1O - cyclic alcohol (maybe aldehyde or ketone)
C_nH_2nO - aldehyde, ketone, cyclic ether (maybe cyclic alcohol)
C_nH_2n+2O - alcohol, ether
C_nH_2n(±1)O₂ - carboxylic acid, ester
C_nH_2n+3N – amine (-NH₂ group)
C_nH_2n-1N – nitrile
C_nH_2n+1NO – amide, C-N=O group

Can anyone think of any others that are common and worth keeping memorized? Or maybe someone has a list ...?

[iamback]

Why do you need to memorize it ?