Conformational effects on the mechanism of acid-catalyzed dehydration of hexitols

Abstract

The Monte Carlo search of the low-energy regions of D-mannitol (4) and D-glucitol (5) conformational space was undertaken in order to investigate conformational effects on the stereochemistry of the acid-catalyzed dehydrative cyclization reaction of 4 and 5 to the corresponding 1,4:3,6-dianhydrohexitols. It was found that although dominant conformations in water resemble closely the crystal state conformations of 4 and 5, the same is not true in solvents of low polarity. The magnitudes of the calculated energies of the reactive conformations for the dehydrative cyclization reaction suggest an S N 2 mechanism with a late transition state.

Selective One-Pot Synthesis of Sorbitans (1,4-Sorbitan and 3,6-Sorbitan) from Glucose via Catalytic Hydrogenation and CO2-Mediated Dehydration

“…The literature is surprisingly poor in theoretical studies , regarding the number of publications that focused on sorbitol dehydration these last decades . Notably, there is a lack of modeling to explain product selectivities, particularly concerning anhydro-sorbitans isomers in the initial sorbitol dehydration.…”

Recent progress in catalytic selective dehydration of sorbitol

“…Dosen-Micovic 和 Cekovic [26] 、 Cekovic [27] 和 Barker [28] 的研究表明, 在酸催化作用下, 山梨醇的转化是通过 均相酸催化剂包括无机酸如盐酸 [28] 和浓硫酸 [25,29] 等, 多相催化剂则包括SiO 2 -Al 2 O 3 [30] , 双 金属催化剂 [31] 和 H 3 PW 12 O 40 /SiO 2 [32] 等 . 另外, 山梨醇在ZnCl 2 熔融 盐介质 [33] 以及高温的液态水中的脱水反应也引起了 人们的关注 [34] .…”