Ring Opening of 2,5-Didehydrothiophene: Structures and Rearrangements of C4H2S Isomers

Autor:	Robert J. McMahon, Yong Seol Kim
Rok vydání:	2005
Předmět:	chemistry.chemical_compound Crystallography chemistry Stereochemistry Organic Chemistry Cumulene Molecule Density functional theory Singlet state Ring (chemistry) Thioketene Carbene Bond cleavage
Zdroj:	The Journal of Organic Chemistry. 70:8171-8179
ISSN:	1520-6904 0022-3263
DOI:	10.1021/jo051395d
Popis:	Electronic structures and rearrangement pathways of several C4H2S isomers are computationally investigated by methods based on coupled cluster theory and density functional theory. Six singlet C4H2S isomers lie within ca. 30 kcal/mol above butatrienethione (6), the apparent global minimum. Ethynylthioketene (7) lies only 2 kcal/mol higher in energy than cumulene 6. Two open-chain isomers, butadiynylthiol (8) and diethynyl sulfide (9), reside ca. 9 and 24 kcal/mol above 6, respectively. Lying 30 kcal/mol above 6, two cyclic singlet isomers, ethynylthiirene (10) and cyclopropenylidenemethanthione (11), are nearly degenerate in energy. Thiophene-2,5-diyl (12) lies substantially higher in energy than 6 (ca. 45 kcal/mol) and is predicted to rearrange preferentially by C-S bond cleavage, leading to thioketene 7, rather than by C-C bond cleavage, leading to diethynyl sulfide (9; retro-Bergman cyclization). Accurate spectroscopic properties of these C4H2S isomers, as well as an understanding of their rearrangement pathways, should facilitate the detection and characterization of these isomers in the laboratory and the interstellar medium.
Databáze:	OpenAIRE
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