Very briefly explain why the reaction of question 1 does not occur in the absence of a strong acid such as H 2 SO 4 . The reaction involves elimination of water from an alcohol to form an alkene. In the absence of acid, the leaving group would be hydroxide ion. This is a very poor leaving group, and in conjunction with the energetically-expensive process of carbocation formation, would not allow the reaction to proceed. Protonation of the alcohol by acid converts the leaving group into water.
Water is an excellent leaving group because it is a neutral molecule.
That water is a superior leaving group helps to overcome the difficulty in forming the carbocation, so the reaction can proceed. Questions 3 and 4 refer to the following reaction. The most likely mechanism for this reaction is E2. Briefly explain your answer to question 3. This is an elimination reaction, so the mechanism choices are E1 and E2.