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I doubted whether I can say cyclobutanal or not. Im confused and didn't found my answer anywhere

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Let's have correct names for related alcohols butanol (e.g. butan-1-ol) and cyclobutanol. Here the -ol suffix means $\ce{-OH}$ group attached to the carbon atom.

In butanal ($\ce{CH3CH2CH2CHO}$), suffix -al means not just $\ce{=O}$ group (oxo group), but entire $\ce{-CHO}$ which already contains carbon, which is included in the counting and numbering. (No locant is needed, because the aldehyde group can be only at the terminal carbon, 1.) If you want to name C-1 to C-4 cyclized butanal, its correct name is cyclobutanone.

Now, it's impossible for cyclic compound to contain aldehyde group in the cycle. For $\ce{-CHO}$ group attached (not included) to the parent cycle, suffix -carbaldehyde is used, therefore names “cyclobutanal” or “cyclobutan-1-al” are wrong, correct is cyclobutanecarbaldehyde.

Fig.1

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  • $\begingroup$ Thankyou mykhal, I've cleared my doubt in nomenclature in both the classroom and here also with this wonderful explanation, thanks alot. Well, is there any more exceptions in naming like this in aldehydes . ? $\endgroup$ Dec 7, 2018 at 11:55
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It's cyclobutanecarboxaldehyde (or cyclobutanecarbaldehyde). I found for you nice little picture of this guy.

enter image description here

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    $\begingroup$ Correct name is cyclobutanecarbaldehyde. There's an instance of "…carboxaldehyde" name in latest IUPAC nomenclature book, but it's a mistake fixed in the ERRATA. $\endgroup$
    – mykhal
    Dec 3, 2018 at 13:49
  • $\begingroup$ Well, here's my real question guys, can't I write it like cyclobutan-1-al. It seems all good with keeping rules in mind , still my teacher got it wrong. $\endgroup$ Dec 3, 2018 at 13:53
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    $\begingroup$ @VishalKumar No, according to the rules, this name does not make sense. $\endgroup$
    – mykhal
    Dec 3, 2018 at 15:14

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