INSERTION REACTION OF CARBOETHOXYLCARBENE TO N-HEXANE IN THE PRESENCE OF BENZOPHENONE AND THE SENSITIZED PHOTO-OXIDATION OF N-HEXANE

In the presence of protosensitizer-benzophenone, ethyl diazoacetate was photolyzedand the resulting carboethoxylcarbene reacted with n-hexane. The result was compared withthat done without the sensitizer. It was revealed that the nature of the insertion products andtheir relative proportions remained the same, whether the sensitizer was presentor not. At the same time, the influence of oxygen on the sensitized and unsensitized inser-tion reaetions was also studied; these showed also no influence on the nature of insertionproducts and their relative proportions no matter whether the sensitizer or oxygen was pres-ent or not. Since oxygen ks a well-known seavenger for the triplet state carbene, the ex-perimental results indicate clearly that the insertion reactions are conducted by the carbenein singlet state. The photo-oxidation products of n-hexane sensitized by air in the presence of benzophe-none were carefully studied, showing that the primary hexyl radical seemed to be rearrang-ed to thermodynamicall     

4-(甲基丙烯酸)2,2,6,6-四甲基哌啶醇酯的合成

合成4-(甲基丙烯酸)2,2,6,6-四甲基哌啶醇酯的方法,在文献上报导甚少,T.Kurosaki 用甲基丙烯酰氯和2,2,6,6-四甲基哌啶醇在苯溶液里,在三乙胺存在下进行反应制得,产率只有27%。     

乙氧羰基甲烯(Carbene)对烷烃的插入反应

本文研究了乙氧羰基甲烯对戊烷、己烷、庚烷和辛烷的插入反应。用色谱-质谱联用法分离并鉴定了插入反应得到的各种异构体,以及测定了在烷烃各位置碳原子上的插入产物的分配比。实验表明在烷烃的各个碳原子上插入产物的分配比例与从反应几率的计算所得的数值不符。文中提出的机理,即经由甲烯夺取氢原子后所生成的碳阳离子或自由基,有一部分重排而后再与乙氧羰基负离子或自由基偶合,可以解释这样的结果。     

烷烃的取代反应——戊烷、己烷和庚烷的溴化

本文用元素溴、N-溴代二乙胺和N-溴代丁二酰亚胺,对戊烷、已烷和庚烷进行光溴化,发现这三种溴化剂所得的溴戊烷、溴已烷和溴庚烷,它们所含异构体的比例都各不相同.其中以2-位异构体含量最多,1-位异构体几乎没有.作者等以溴分子的活性与烷基自由基移位进行解释,并与光照氯化结果相比较,氯化由于氯比较活泼,自由基来不及转位,即与氯反应,因而1-位异构体含量多。     

SUBSTITUTION REACTIONS OF ALKANES——BROMINATION OF PENTANE,HEXANE AND HEPTANE

In the photo-bromination of pentane, hexane and heptane with bromine, N-bromo-diethylamine or N-bromo-succinimide, the authors found that the mono-bromo-pentanes, -hexanes and-heptanes obtained contain the isomers in the same proportions disregarding whatever brom-inating reagent is used. Among the isomers, 2-bromo-compounds occur in dominant quantitieswhile 1-bromo-compounds are nearly nil. The authors attributed these phenomena mainly tothe low mobility of bromine molecules but the rearrangement of the alkyl free radicals fromprimary to the secondary. Compared with chlorination, chlorine molecules are more mobileand combine with alkyl free radicals rather rapidly before rearrangement occurs, which makes1-chloro-isomer more abundant.     

光敏剂存在下乙氧羰基甲烯对己烷的插入反应和己烷的光敏氧化

本文对光敏剂二苯甲酮存在下,重氮乙酸乙酯光解所产生的乙氧羰基甲烯对已烷的插入反应进行了研究,并与无光敏剂时的插入反应进行了比较.发现光敏剂的存在不影响插入产物性质和它们的分配比例.同时,发现作为三线态猝灭剂的氧的存在对这些反应也没有影响.这些实验结果表明,对己烷的插入反应是由单线态的乙氧羰基甲烯进行的.对在二苯甲酮存在下已烷被空气光氧化的产物进行了仔细的分离和鉴定.结果表明,得到的是2-位和3-位已基自由基偶联和氧化的产物,因此看来,伯位的已基自由基在进行偶联和氧化反应之前先要转位成热力学上比较稳定的仲位自由基。     

INSERTION REACTIONS OF CARBOETHOXYCARBENE TO ALKANES

The insertion reactions of carboethoxycarbene on n-pentane, n-hexane, n-heptane and n-octane are studied. The products of each of the reactions were separated and identified by gaschromatography-mass spectrometry. The ratio between the products inserted on various C-atoms in each reaction is not coincident with that calculated from the reaction probability.This can be explained by a suggested reaction mechanism, in which the carbonium ion or freeradical, first formed during the abstraction of H-atom by the carbene, will rearrange partial-ly before recombination with the carboethoxy-methyl anion or free radical.