Hydrogen-bond basicity of secondary and tertiary amides, carbamates, ureas and lactams
1992; Royal Society of Chemistry; Issue: 12 Linguagem: Inglês
10.1039/p29920002091
ISSN2050-8239
AutoresJean‐Yves Le Questel, Christian Laurence, Abdeljalil Lachkar, Maryvonne Helbert, M. Berthelot,
Tópico(s)Chemical Reaction Mechanisms
ResumoThe hydrogen-bond basicity scale pKHB(logarithm of the formation constant of 4-fluorophenol–base complexes in CCl4) has been measured for tertiary and secondary amides, carbonates, ureas and lactams. The hydrogen-bonding fixation site is the carbonyl group, even for the very hindered amide ButCON(C6H11)2. In the amides R1CONR2R3 the hydrogen-bond basicity is decreased more by bulky R1 substituents on the carbonyl carbon than by bulky R2 and R3 substituents on nitrogen. The field effect of X substituents operates more effectively on hydrogen-bond basicity than the resonance effect in the XCONMe2 series. The hydrogen-bond basicity is increased by six-membered cyclisation.
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