Synthesis of new kinetic gas hydrate inhibitors : lactams as nucleophiles

Abstract

Lactam-based surfactants have been synthesized using amines with different chain lengths. Most reactions were also carried out with lactams of different ring sizes: 5, 6 and 7-member ring (pyrrolidone, piperidone and caprolactam respectively). Long chain amines with 18, 16 and 12 carbon atoms were used during the final amidation reaction. This provided a series of final products with different ring sizes and different chain lengths. Nine different lactam-based surfactants were synthesized during this project. The yield of the final product varied according to the ring sizes used, with the 6 member ring products having a 100% yield for all 3 long chain amines. The 5 member ring products had a 92% yield, while the 7 member ring was 73% yield on average. 1HNMR analysis showed some starting materials left in the product. In some cases up to 50% starting material did not react, which accounts for the relatively high yield of the final products. The production of esters using lactams as starting material and the subsequent hydrolysis of the produced ester had the same reaction yield of 65% for both reactions. The reaction sequence used for the transformation of starting material to final product is shown in scheme 1 below. Other strategies to produce lactam-based surfactants were investigated. Attempts to use anhydrides and Dodecenyl Succinic Anhydride (DDSA) failed. Another reaction that was investigated is the “on water” reaction which direcly tranforms esters to amides. This reaction worked for short chain amines (butylamin) but did not proceed for long chain amines with 12 carbon atoms and above.

Scheme 1. Reaction pathway for the 9 KHI produced.