A Review of Infrared Spectra from Wood and Wood Components Following Treatment with Liquid Ammonia and Solvated Electrons in Liquid Ammonia

Abstract

ABSTRACT The chemical changes that occur in wood and wood components (cellulose, holocellulose and lignin) following treatment with liquid ammonia and solvated electrons (e− s,) in liquid ammonia have been investigated using FTIR spectroscopy. When ammonia penetrates into a wood structure, all carboxylate groups will react with ammonia to form ammonium salts, aldehydic and ketonic groups will follow a similar reaction to produce imines, and ester groups will react to forni amides. After treatment with (e− s) in liquid ammonia, wood samples show diminished absorption around 15 13 cm−1, a position corresponding to aromatic groups, and diminished absorption peaks associated with aldehydic, ketonic, and ester groups. The overall changes in the IR spectra of cellulose in liquid ammonia and (e− s) in liquid ammonia are not dramatic. The IR spectra of the isolated holocellulose after treatment with (e− s) in liquid ammonia have intensities and band shape similar to those of cellulose. The isolated lignin behaves in a manner similar to wood, in that the liquid ammonia causes some decrease in the intensities of absorptions associated with C-O and C=O bands, and increase in strength of the amide functional group at 1600 cm−1. The resulting extracts of wood, following treatment with (e− s) in liquid ammonia, appear to loose their “aromaticity”. Because wood has long been used, and still is used extensively as an important constructional material, the changes in mechanical characteristics caused by the action of various reducing agents appears to have been an important area of scientific interest. The following review focuses on the chemical changes in the functional groups of the surface moieties of wood when treated with a reducing agent, such as (e− s + NH3liq), using infrared spectroscopy.