Catalysis by hydrogen chloride in the gas‐phase elimination kinetics of 2‐phenyl‐2‐propanol and 3‐methyl‐1‐buten‐3‐ol

A homogeneous, molecular, gas-phase elimination kinetics of 2-phenyl-2-propanol and 3-methyl-1- buten-3-ol catalyzed by hydrogen chloride in the temperature range 325-3868C and pressure range 34-149 torr are described. The rate coefficients are given by the following Arrhenius equations: for 2-phenyl-2-propanol log k1 (s � 1 ) ¼ (11.01 � 0.31) � (109.5 � 2.8) kJ mol � 1 (2.303 RT) � 1 and for 3-methyl-1-buten-3-ol log k1 (s � 1 ) ¼ (11.50 � 0.18) � (116.5 � 1.4) kJ mol � 1 (2.303 RT) � 1 . Electron delocalization of the CH2 —CH and C6H5 appears to be an important effect in the rate enhancement of acid catalyzed tertiary alcohols in the gas phase. A concerted six-member cyclic transition state type of mechanism appears to be, as described before, a rational interpretation for the dehydration process of these substrates. Copyright # 2007 John Wiley & Sons, Ltd.