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The pKa of an α hydrogen is 20.

NOTE: Where did that pKa come from? Is it aliphatic or aromatic, as benzaldehyde would stand to have a lower pKa (as it is more acidic that the aliphatic version).

Benzaldehyde has no alpha proton, so it is not acidic, do you mean phenylacetaldehyde? I don't have the source of this value to hand, but I do have a reference for 3-pentanone as pKa 19-20 in water. See here I suspect that the higher figure you have seen is in DMSO, where pKa values are usually higher than in water. Walkerma 21:01, 20 September 2005 (UTC)

how does an organism metabolize an aldehyde?


in the wikipedia article on the "IUPAC nomenclature of organic chemistry" it is stated that (quote): " If a prefix form is required, "oxo-" is used (as for ketones), with the position number indicating the end of a chain: 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: C6H11CHO is cyclohexanecarbaldehyde. "

This article doesn't mention the prefix "oxo-" at all. Instead only: " If another functional group is present which IUPAC rules prescribe must be named as a suffix, the aldehyde group is named with the prefix formyl-. This prefix is preferred to methanoyl-. "

This would imply that either this article on aldehydes misses out important information, or that the above quoted article on IUPAC nomenclature is misleading.

In any case there is a lack of clarity. Could somebody more qualified please look into this? —The preceding unsigned comment was added by (talkcontribs) 20:45, 11 June 2007 (UTC)

The Aldehyde article has been revised. Spacepotato 09:26, 4 August 2007 (UTC)

acyl vs aldehyde[edit]

Are they exactly the same thing? 15:12, 22 September 2007 (UTC)

No, they are different - rather like the difference between alkyl and alkane. So you could talk about the acyl group in acetic acid, meaning the CH3C(=O)- group, commonly called the acetyl group. Walkerma 15:38, 22 September 2007 (UTC)

What is a semialdehyde?[edit]

What is a semialdehyde, have seen it e.g. here: Succinic_semialdehyde ChristianBxx 16:05, 22 October 2009 (UTC) —Preceding unsigned comment added by Christian75 (talkcontribs)

A simple internet search reveals that it is the monoaldehyde of a dicarboxylic acid. -- (talk) 05:20, 27 June 2013 (UTC)


The Aldol Condensation and Canizzaro reactions need more coverage here since they are important reactions concerning Aldehydes. Could someone please pick excerpts and put them here? 02:09, 8 April 2010 (UTC)Darshit —Preceding unsigned comment added by Darnir redhat (talkcontribs)

Merger proposal[edit]

I propose that Dialdehyde be merged into Aldehyde. I think that the content in the dialdehyde article can easily be explained in the context of aldehyde, and the aldehyde article is of a reasonable size in which the merging of dialdehyde will not cause any problems as far as article size or undue weight is concerned. Roshan220195 (talk) 18:08, 29 March 2012 (UTC)

Unsaturated aldehyde[edit]

This phrase comes up a bit, and is used in this article on Coriander, NPR story about how people taste cilantro/coriander (December 2008). Should this be defined here more specifically?(mercurywoodrose) (talk) 03:32, 24 September 2012 (UTC)

Assessment comment[edit]

The comment(s) below were originally left at Talk:Aldehyde/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Chemistry is not my expertise but....

is this quoted text misleading? (chemical formula O=CH-) ?should it instead read as?: (chemical formula O=C-H)

Electricmic 21:07, 26 September 2007 (UTC)

Last edited at 21:07, 26 September 2007 (UTC). Substituted at 07:08, 29 April 2016 (UTC)