Correlation of heats of combustion with empirical formulas for fatty alcohols
Gross heats of combustion (Hg) for the homologous series of saturated fatty alcohols C10–C22 were measured in a Parr adiabatic calorimeter according to ASTM D240 and D2015. The measured values for these alcohols ranged from 1582 to 3453 kg-cal/mole. We developed equations that related carbon number (CN) or chain length, electron number (EN) or number of valence electrons and molecular weight (MW) to calculated Hg by linear regression analysis (LINREG). These equations are: Hg=26.00+155.60 CN; Hg=26.00+25.94 EN; and Hg=−172.2+11.00 MW. R squared values for all three equations were 0.99. The results obtained with LINREG were compared to a literature method. Comparisons were made for both the fatty alcohols above and C1–C5, C7, C8 and C16 alcohols of the literature method. For the former alcohols there was no difference in accuracy or precision between the two methods. For the latter alcohols LINREG was both more accurate and precise. Measured Hg vs. chain length for C1–C22 alcohols showed a perfect linear relationship. Thus, knowing chain length, Hg can be predicted accurately for alcohols in this range.
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