The nature of rotational barriers of the C-N bond in thioamides and the origin of the nonplanarity for thiourea

Woong Kim, Ho Jin Lee, Young Sang Choi, Jong-Ho Choi, Chang Ju Yoon

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

The most important donor/acceptor interactions about the C(O)-N bond rotation in formamide are the barrier-forming N(lp)/C-O(π)* interaction and the antibarrier-forming N(lp)/C-O(σ)* interaction. There is a large difference between the rotational barriers of formamide and urea. The most significant causes which lead to the low rotational barrier of urea are the reduction of the barrier-forming N(lp)/C-O(π)* interaction energy and the existence of the antibarrier-forming N′(lp)/C-O(π)* interaction. The nonplanarity of the ground state for urea is caused by the competition of the two former interactions. They come into conflict with each other to a greater extent in the planar structure than in the nonplanar structure and this excessive conflict results in the instability of the planar structure. To relax this strain, the geometry is transformed into a stable nonplanar one. We found that the same interpretation as for formamide is applied to the thioamide system. The amide π-orbital system was investigated to understand the change in the C-N and C-O(S) bond length during the rotation process.

Original languageEnglish
Pages (from-to)2663-2668
Number of pages6
JournalJournal of the Chemical Society - Faraday Transactions
Volume94
Issue number18
Publication statusPublished - 1998 Dec 1

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Thioamides
Thiourea
thioureas
Urea
ureas
planar structures
Bond length
interactions
Amides
Ground state
Geometry
amides
formamide
orbitals
ground state
causes
geometry

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

The nature of rotational barriers of the C-N bond in thioamides and the origin of the nonplanarity for thiourea. / Kim, Woong; Lee, Ho Jin; Choi, Young Sang; Choi, Jong-Ho; Yoon, Chang Ju.

In: Journal of the Chemical Society - Faraday Transactions, Vol. 94, No. 18, 01.12.1998, p. 2663-2668.

Research output: Contribution to journalArticle

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