十二酸的α-氯代反应中的催化剂研究

Investigation of catalysts in α-chlorination of dodecanoic acid

α-氯代脂肪酸是一类可用于直接从脂肪酸合成α-氨基酸和甜菜碱类两性表面活性剂等精细化学品的重要中间体。本文从烯酮式反应机理出发,以α-氯代十二酸(α-CDA)的合成为模型,对酰氯化试剂(对甲苯磺酰氯、十二酰氯、氯磺酸等)和质子酸催化剂(如H型离子交换树脂、氯磺酸、对甲苯磺酸、醋酸等)进行组合和选择,并与文献报道的特殊添加剂乙酐比较,研究不同催化体系在酸催化合成α-氯代脂肪酸时的催化作用。氯磺酸既有磺酸基团提供强质子酸,又有磺酰氯基团作为酰氯化试剂,因而是催化十二酸的α-氯代反应的适宜催化剂。当w(氯磺酸)∶w(十二酸)=2%,搅拌转速1000r/min,氯气流量40L/h,反应温度为120℃时,反应3h后α-CDA产率达到96.4%。

α-Chloro-fatty acids are important intermediates employed for synthesizing fine chemicals such as α-amino acids and betaine-like amphoteric surfactants. In this paper, the effects of different catalyst combinations on the synthesis of α-chloro-dodecanoic acid （α-CDA） were investigated, in which a series of acyl chlorides （such as 4-toluene sulfonyl chloride, dodecanoyl chloride, chlorosulphonic acid, etc. ） , proton acids （such as H type cation exchange resin, chlorosulphonic acid, 4-toluene sulfonic acid, acetic acid, etc. ） and their combinations were tested with acetic anhydride as a reference. Chlorosulphonic acid was found to be the best among the assayed catalysts due to its acyl chloride and strong proton acid moieties. The yield of α-CDA reached 96.4% in 3 h under the optimized reaction conditions： w（chlorosulphonic acid） ： w（dodecanoic acid） =2%, 1000 r/min, and chlorine 40 L/g at 120 ℃.