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In both Sn1 and Sn2, the leaving group is very important. In alkyl halides the leaving group is a halogen, but there can be other leaving groups as well. In general, the more stable the leaving group, the more willing it is to accept a pair of electrons. This is not too different from the explanation about strong acids. A strong acid has a weak conjugate base. The weak base is willing to accept a pair of electrons, and is able to stabilize the negative charge. The weak base can be thought of as a good leaving group. a) In each pair, indicate which the better leaving group (weaker base) is. You will need to consult table 4.1 on page 179 in your textbook, 8th edition. Clor NH, or -NH2 H20 or OH H2O or H2S (HINT: you will need to remember periodic trends in basicity to answer this one). b) Which of the following molecules contain a good leaving group (imagine breaking the bond between a carbon and the bolded group attached to it and remember a good leaving group is a weak base)? Briefly explain your choice(s). NH2 CH3CH2CH_Br CH3CH2 CH,CH, OH © H NH c) Which of the following Sn2 reactions will take place as written? (HINT: Consider the stability of the anions on each side of the equation.) Explain your choices. OH + 1 + "он CH,CH! + HS CH3CH,SH + 1 NH2 + HN Br OH + HO CN 3 CN