Premium
Thermodynamic data for hydrogen bonding of thiols with Lewis bases in carbon tetrachloride. Weak association by the PMR method
Author(s) -
Hu Siung J.,
Goldberg Edward,
Miller Sidney I.
Publication year - 1972
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270040508
Subject(s) - chemistry , carbon tetrachloride , lewis acids and bases , hydrogen bond , hydrogen , base (topology) , crystallography , medicinal chemistry , molecule , organic chemistry , catalysis , mathematics , mathematical analysis
Data for 30 hydrogen bonding pairs taken from the alkanethiols, i ‐C 3 H 7 SH, n C 3 H 9 SH and t ‐C 4 H 9 SH, and 16 bases have been obtained by a PMR method. Representative data for i ‐C 3 H 7 SH at 304 ± 2°K are (base, 10 2 K in M −1 , –Δ H ° in kcal/mole): (CH 2 ) 4 S, 3·1, 0·8; (CH 3 ) 2 S, 3·0, 0·9; (CH 3 ) 2 S 2 , 3·7, 0·5; (CH 3 ) 2 CO, 4·7, 0·9; CH 3 COOC 2 H 5 , 5·7, 1·1; (CH 2 ) 4 O, 6·1, 1·0; HCON(CH 3 ) 2 , 12, 0·9; (CH 3 O) 2 SO, 12, 0·9; (C 2 H 5 O) 3 PO, 6·5, 1·0; CH 3 (CH 3 O) 2 PO, 18, 1·0; ((CH 3 ) 2 N) 2 CO, 5·9, 1·1; CH 3 CN, 13, 0·6. In essence, the problems and errors involved in obtaining equilibrium data for weak complexes stem from the limited concentration rangethat is accessible. This leads to large uncertainties in the quantities K , Δ H ° and Δ S °. Structural effects on hydrogen bonding at the sulfur site, both as Lewis acid or base, are discussed. Two erroneous PMR methods in the literature used for assessing the strength of hydrogen bonds are pointed out.