Current Applications And Development Of Catalyst For The Synthesis Of Essay

Current Applications And Development Of Catalyst For The Synthesis Of Highly Functional Organic Carbonates - Essay Example An exhaustive review on the catalytic production of organic carbonates is lacking. The conventional procedure for synthesis of organic carbonates earlier involved toxic halogen compounds or phosgene, and later on moved to non toxic compounds such as carbon dioxide, alcohols, and epoxides. Recent catalysts include palladium, salen ligands, DBU, transition metal halides such as NiCl2, Lewis bases like Re(CO)5Br, NHC-CO2 adducts, tin, and Cu-exchanged zeolite Y catalyst. Introduction Organic carbonates are organic compounds obtained by carbonic acid and hydroxyl compound diesterification (1). The carbonates are produced in the form of diaryl, dialkyl or substituted dialkyl dialyl products depending on the type of hydroxyl compound used in the diesterification reaction. Organic carbonates have a wide variety of industrial, medical and biological applications (2). More specifically, they are used as intermediates, solvents and protective groups during the synthesis of lubricants, pharmace uticals, herbicides, pesticides, plastics, etc. (3). Of the different kinds of organic carbonates, dimethyl carbonate is the simplest one, produced industrially from methanol through catalytic oxycarbonylation (1). A review of the literature on the catalytic production of organic carbonates reveals that comprehensive reports on the development of catalysts in the synthesis of organic carbonates is lacking. While earlier, organic carbonate synthesis with the help of catalysts required halogen compounds or phosgene, research on the synthesis of organic compounds later on was more inclined towards substituting halogens with other non toxic compounds. In recent years, research has focused on synthesizing organic carbonates from carbon dioxide, alcohols, and epoxides. Organic carbonate synthesis has thus seen a new dawn, wherein more emphasis was on green chemistry and use of reagents that are least toxic to the environment and to living organisms. The present paper aims at understanding how the use of catalysts in synthesizing organic carbonates progressed over the years. For this purpose, research reports on organic carbonate synthesis will be analyzed and discussed. The types of catalysts employed in organic carbonate synthesis will also be reviewed. The aim is to study the development of catalysts for organic carbonate synthesis, especially in the recent years. Theoretical Background Organic carbonates are formed by the diesterification of hydroxyl compounds with carbonic acid. Carbonic acid does not exist in free state. Its monoester is called hemicarbonic acid and it is formed by the reaction of carbon dioxide with alcohol. It can only be isolated in the form of salts and simple/mixed anhydrides with carboxylic acids because of its unstability. Through the esterification of hemicarbonic acid with hydroxy compounds, organic carbonates can be synthesized. These are classified into two main groups, saturated and unsaturated organic carbonates. Unsaturated carbon ates include symmetrical (e.g. diallyl carbonate) and unsymmetrical (e.g. allyl methyl carbonate) organic carbonates. Saturated organic carbonates are further divided into several other categories that include aliphatic, aliphatic aromatic and aromatic. Further classification of organic carbonates is given in figure 1. Dimethyl carbonate is the simplest organic carbonate. Figure 1: Classification of Carbonates (1) Shaikh and Sivaram provided a comprehensive review of the various processes of organic carbonate synthesis. Since then, many more developments have taken place in the field. Before discussing the latest developments in organic carbon