Is benzene carbaldehyde a correct name for Benzaldehyde? I'm (always) getting confused between common and IUPAC names. If the above name is correct then is it a common one or IUPAC? And why don't we use it more often?


Both are IUPAC names, but used in different situations. For a 1 carbon aldehyde attached to a benzene, the one that must be used is benzaldehyde.

Aldehydes ($\ce{R-CHO}$) take the suffix "-al". If other functional groups are present, the chain is numbered such that the aldehyde carbon is in the "1" position, unless functional groups of higher precedence are present.

If a prefix form is required, "oxo-" is used (as for ketones), with the position number indicating the end of a chain: $\ce{CHOCH2COOH}$ is 3-oxopropanoic acid. If the carbon in the carbonyl group cannot be included in the attached chain (for instance in the case of cyclic aldehydes), the prefix "formyl-" or the suffix "-carbaldehyde" is used: $\ce{C6H11CHO}$ is cyclohexanecarbaldehyde. If an aldehyde is attached to a benzene and is the main functional group, the suffix becomes benzaldehyde.

For example, this guy would be cyclohex-2-ene-1-carbaldehyde:

enter image description here

| improve this answer | |

Both names, ‘benzenecarbaldehyde’ and ‘benzaldehyde’, are unambiguous and describe the same compound. However, the preferred IUPAC name (PIN) is ‘benzaldehyde’.

Concerning aldehydes, the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) reads as follows:

P-66.6.1 Systematic names of aldehydes

Aldehydes are systematically named in three ways:

(1) substitutively, using the suffixes ‘al’ for $\ce{-(C)HO}$ and ‘carbaldehyde’ for $\ce{-CHO}$;

(2) by changing the ‘ic acid’ or ‘oic acid’ endings of retained names of carboxylic acids into ‘aldehyde’; the nomenclatural properties of acids are transferred to aldehydes; thus, preferred names of aldehydes correspond to preferred names of acids, and carboxylic acids that are not substitutable generate nonsubstitutable aldehydes;

(3) by using the prefixes ‘oxo’, denoting $\ce{=O}$, or ‘formyl-’, denoting the substituent group $\ce{-CHO}$.

In particular,

P- The suffix ‘carbaldehyde’ is used when the $\ce{-CHO}$ group is attached to a carbon atom of a ring or ring system, or to a heteroatom.

For example, ‘cyclohexanecarbaldehyde’ is a PIN.


However, according to P-, the PIN for the compound given in the question is ‘benzaldehyde’. (This name is analogous to the preferred name of the corresponding acid ‘benzoic acid’, see P-66.6.1 (2) above.)


Nevertheless, according to P-, the PINs for phthalaldehyde and terephthalaldehyde are the systematic names ‘benzene-1,2-dicarbaldehyde’ and ‘benzene-1,4-dicarbaldehyde’, respectively. (These names are analogous to the preferred names of the corresponding acids ‘benzene-1,2-dicarboxylic acid’ [not ‘phthalic acid’] and ‘benzene-1,4-dicarboxylic acid’ [not ‘terephthalic acid’], respectively.)

benzene-1,2-dicarbaldehyde   benzene-1,4-dicarbaldehyde

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.