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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Nescafe on March 17, 2014, 09:58:30 AM

Title: CycloPropyl v.s. Cyclobutyl
Post by: Nescafe on March 17, 2014, 09:58:30 AM
Hello,

I am really confused as to why 1) cyclopropyl has SP2 character, is it because of the strain of the ring that forces the orbitals to adopt a SP2 character? 2) does cyclobutyl and cyclpentyl also have this character or is the strain/thus the bond angles allow for a SP3 character.

Also would anyone know why SP3 carbons are prone to metabolic oxidation whilst SP2 carbons are metabolically resilient? I can not find anything on this online.

Many thanks in advance,

Nescafe.
Title: Re: CycloPropyl v.s. Cyclobutyl
Post by: Babcock_Hall on March 17, 2014, 10:43:55 AM
The sp2 carbons of an aldehyde are easily oxidized metabolically.  The sp2 carbons of an alkene are usually hydrated before oxidations.
Title: Re: CycloPropyl v.s. Cyclobutyl
Post by: Nescafe on March 17, 2014, 01:22:16 PM
The sp2 carbons of an aldehyde are easily oxidized metabolically.  The sp2 carbons of an alkene are usually hydrated before oxidations.

Thanks for your reply. I am not referring to alkenes but cylic alkanes such as cyclobutyl and cyclopentyl.

We were taught that cyclohexane is prone to metabolic oxidation by Phase I processess and that replacement by smaller strained rings prohibits this. Never was I taught why nor can I find an explanation. I was wondering, do cyclobutyl and pentyl also have SP2 character like cyclopropyl?

Thanks,

Nescafe.
Title: Re: CycloPropyl v.s. Cyclobutyl
Post by: sandwich4 on March 17, 2014, 08:39:35 PM
The standard explanation is that the tight bonds such as the C-C bonds in cyclopropane require more p character. This would mean that the C-H bonds on a carbon in cyclopropane would be more s character (i.e. more sp2 than sp3). I believe that cyclopentane is a very stable ring which uses sp3 hybridization on the carbons. Cyclobutane is probably in between.