Although the reaction shown in eq. 7.26 occurs faster than that shown in eq. 7.28, the yield of product is lower. The yield of t-butyl chloride is only 80%, whereas the yield of n-butyl chloride is nearly 100%. What by-product is formed in eq. 7.26, and by what mechanism is it formed? Why is a similar by-product not formed in eq. 7.28?