RESEARCH ARTICLE

 

Part II: Ab initio and NMR investigations into the barrier to internal rotation of various oxo- and thio- analogues of 2-Oxo-2H-chromen-7-yl dimethylcarbamates

 

 

Caryl K.A. Janse van Rensburg; Ross S. Robinson^*; Hendrik G. Kruger

Warren Research Laboratory, School of Chemistry, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg, 3209 South Africa

 

 

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ABSTRACT

A range of 2-oxo-2H-chromen-7-yl dimethylcarbamates were synthesized as described in part I of this publication, containing either an oxygen or sulphur a to the carbonyl or thiocarbonyl group of the amide moiety. Variable temperature and exchange spectroscopy NMR was performed on these compounds and the barrier to free amide rotation was calculated. Each of these compounds were also modelled ab initio and the gas phase barrier to rotation calculated. These three sets of data were compared and the influence of the a-heteroatom on rotation for amides and thioamides evaluated.

Keywords: Thiocarbonyl, amide, rotational barrier

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Full text available only in pdf format.

 

 

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Received 13 December 2010
Revised 15 February 2011
Accepted 20 June 2011

 

 

Submitted by invitation to celebrate 2011 the 'International Year of Chemistry'.
* E-mail: robinsonr@ukzn.ac.za