: ETHYLCELLULOSE : ethoxyl content 49% : Scientific Polymer Products, USA : suspension in methanol; 10 yg
: Teq 510°C; ty 5s; tj 10s; Eel 12eV; expansion chamber removed (Extranuclear 5000-1 Py-MS system)
REMARKS - At first sight this spectrum appears to be quite different from that of cellulose (Spectrum A.l) because of the dominance of odd numbered mass peaks and the prominent signals in the high mass range. Obviously many pyrolysis products now possess an ethoxyl group instead of a hydroxyl group. Also, the presence of the ethoxylgroups significantly reduces the otherwise dominant dehydration reactions. Therefore, the peaks at m/z 172 and 200 can be rationalised as the mono-ethylated and diethylated analogues of anhydrolevoglucosan (normally at m/z 144) respectively, whereas the peaks at m/z 143 and 171 may then represent the (M-29) fragments. Interestingly, ethylation (gain of 28 daltons) followed by the loss of an ethyl radical (29 daltons) results in the net loss of 1 dalton. Thus, some of the major odd mass peaks may well correspond to the next higher mass peak in the normal cellulose spectrum, e.g. m/z 31 vs. 32, m/z 59 vs. 60, m/z 97 vs. 98, m/z 125 vs. 126. Furthermore, pyrolytic degradation of the ethoxyl groups may result in the elimination of ethene (m/z 28) and ethanal (m/z 44) respectively. Such pyrolytic eliminations may explain the occurrence of the marked peaks at m/z 156 (m/z 200 - 44) and 112 (m/z 200 -2 X 44).
This Page Intentionally Left Blank
Was this article helpful?