Conformational equilibria and infrared matrix isolation spectra of bromoacetyl chloride and bromoacetyl bromide

摘要

Abstract: IR spectra of the title compounds were investigated in argon and nitrogen matrices at 14 K with nozzle temperatures from 313 to 900 K. After annealing to 30 - 34 K the spectra changed considerably and the high energy conformer (gauche) nearly vanished. The matrix spectra supported the assignments into anti and gauche conformer bands, based upon bands disappearing on crystallization, and due to the small band widths various instances of overlapping bands were detected. Raman spectra were recorded as liquids at various temperatures and as amorphous and crystalline solids. The matrix spectra recorded at different nozzle temperatures gave as an average $Delta@H$+O$/ (gauche - anti) $EQ 1.7 $POM 0.6 in bromoacetyl chloride and 2.9 $POM 0.6 kJ mol$+$MIN@1$/ in bromoacetyl bromide which are lower than in isothermal vapor cells, indicating that the high energy conformer (gauche) was partly converted to anti during deposition. The corresponding $Delta@H$+O$/ values in the liquid (Raman) were 4.7 $POM 0.4 and 6.6 $POM 0.4 kJ mol$+$MIN@1$/, respectively. !8