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1.在以正丙醇及正丁醇为试剂进行对二甲苯及对称三甲苯的烷基化反应中,证明在70—80°及80％硫酸的催化下,伯烷基实际上全部异构化为相应的仲烷基。 2.根据产物中异构体的相对含量,计算在邻二甲苯烷基化时生成1,2,3-异构体与生成1,2,4-异构体两反应活化自由能差(△F(?)—△F(?))。无论所用的试剂为伯醇或仲醇,在75°进行异丙基化时,算得数值为1.2千卡/克分子,仲丁基化时为1.6千卡/克分子;以异丁醇为试剂进行叔丁基化时两反应活化自由能差约为2.9千卡/克分子。 3.文中讨论对二甲苯及对称三甲苯进行叔丁基化时的空间位阻。此外尚列有二甲苯和三甲苯的若干烃基取代物之物理常数。
1. Alkylation of p-xylene and symmetric trimethylbenzene with n-propanol and n-butanol proved that the primary alkyl groups were virtually all isomerized under the catalysis of 70-80 ° and 80% sulfuric acid Into the corresponding secondary alkyl. According to the relative content of the isomers in the product, calculate the difference in the free activation energy between the formation of the 1,2,3- isomer and the 1,2,4-isomer when the o-xylene is alkylated F (?) -? F (?)). Irrespective of the reagents used, primary or secondary alcohols, when isopropylated at 75 °, gave a value of 1.2 kcal / mol and 1.6 kcal / mol during sec-butylation. Using isobutanol as reagent Tertiary butylated reaction activation free energy difference of about 2.9 kcal / mole. In this paper, we discuss the steric hindrance of tert-butylation of xylene and symmetric trimethylbenzene. In addition, the physical constants of several hydrocarbon substituents of xylene and trimethylbenzene are listed.