REAÇÃO DE CONDENSAÇÃO DO GLICEROL COM COMPOSTOS CARBONÍLICOS. SÍNTESE, CARACTERIZAÇÃO E APLICAÇÃO EM CRISTAIS LÍQUIDOS

• Main Authors: Jacqueline Kautz, Willian Feltrin, Eric S. Sales, Vera Lucia Eifler-Lima, Aloir A. Merlo
• Format: Article
• Language: English
• Published: Sociedade Brasileira de Química 2015-09-01
• Series: Química Nova
• Subjects: glycerol derivatives; condensation reaction; heterogeneous catalyst; liquid crystals; solketal transformation
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-40422015000801053&lng=en&tlng=en

Condensation reactions of glycerol with aldehydes and ketones were performed under thermal heating and microwave irradiation regimes. Homogeneous and heterogeneous catalysts were tested in both conditions. A silica sulfated (SiO2-SO3H) heterogeneous catalyst demonstrated the best performance relative to a selectivity of >95% in favor of 5-membered ketals. For acetals, preference in favor of 5-membered or 6-membered functional groups depends on the nature of the catalyst. Homogenous catalysts favor the more stable 6-membered acetals, whereas heterogeneous catalysts favor the less stable 5-membered acetals. However, the isomer ratios in the acetalization reaction are too low, and hence the reaction cannot be used in a synthetic plan for functional materials. Ketalization processes mediated by SiO2-SO3H show a high selectivity in favor of a 5-membered ring (1,3-dioxolane). The scope of condensation was tested with different ketones. A mechanism for heterogeneous catalysis related to the selectivity in the cyclization process is presented herein. Solketal, a commercial product, was also obtained by a condensation reaction of glycerol and propanone, and showed a high selectivity in favor of 1,3-dioxolane. It was transformed to potential allylic and chiral intermediates. A mesogenic core was connected to the organic framework of glycerol to produce a monomer liquid crystal material with a stable smectic-C mesophase.