Basic Organic Nomenclature

An Introduction

Dave Woodcock,
Associate Professor Emeritus UBC (Okanagan)
©1996,2000, 2008

5. Functional Groups
with Suffix or Prefix

V Alkanals


Atomic grouping
Position in chainonly at
end of chain
General formula CnH2nO
Common family name aldehyde


  • When writing the -al suffix (alkanal) make absolutely sure that it is distiguishable from -ol (alkanol).
    If necessary, PRINT the 'o' or the 'a'.

  • Since the suffix (-al) has an initial vowel, the terminal -e of the alkane name is dropped before the suffix is added.

  • The carbonyl group in tha alkanal (aldehyde) family is always at the end of a carbon chain. It is this feature which makes it chemically distinguishable from the carbonyl in any other position in the carbon chain: hydrogen atoms linked to a carbon which is also linked to an oxygen atom (either singly or doubly) are readily oxidizable. Thus a major distinguishing feature between these two carbonyl-containing compounds is that alkanals are readily oxidized, alkanones are not.

  • Since the carbonyl group is at the end of the chain, this is always position 1 when it is the principle group (i.e. when the suffix is being used) and the locant is omitted:
    pentanal, NOT pentan-1-al.

    However, if the oxo prefix is being used, the locant must also be used, since oxo is used for a carbonyl group anywhere in the chain.

    Examples :

    StructureIUPAC NameModel
    methanal (aka formaldehyde)

Self Assignment Questions
Review Alkanones

Next page : Alkanamides.


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