氯或溴甲基化

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Theoptimumconditionswhichwedevelopedforthechlorornethylationofbenzeneinvolvedthereactionof3moiolesofbenzene,2equivalentsoftrioxymethyleneand30g.ofzincchloridein200ml.ofglacialaceticacidwithexcessanhydroushydrogenchloride(passedintosaturationduringthefirst3hours)at60℃for72hours.Theyieldofbenzylchlorideis65%,basedonformaldehyde.Toluenewasmuchmorereactive-a57%yieldoftheproductwasobtainedinonly18hourswithhalfthequantityofthezincchloridecatalyst.IneaseofmanipulationandqualityofproducttheprocedureprovedquiteadvantageousoverthatdescribedbyBlancJAC.Toastirredmixtureoftheether4(10.0g,0.05mol)andparaformaldehyde(1.5g,0.05mol)inhexane(100ml)wasaddeddropwiseconc.HCl(50ml)atroomtemperature.Afterthesolidwasdissolvedcompletely,themixturewasstirredforanother30minandthenstoodstill.Thetwolayerswereseparated.Theaqueouslayerwasextractedwithhexane(250ml)again.Theorganiclayerandtheextractswerecombined,washedwithbrine,dried,andevaporatedinvacuo.Silicagelchromatographyoftheresidueprovidedthebenzylchloride5ascolorlessoilin90%yield(11.1g).在三口瓶中加入32mL36％(0.42mo1)甲醛水溶液,41mL(0.42mol)水杨醛和270mL浓盐酸，冷却搅拌下通人干燥的HC1气体，保持温度在l5～20℃，约2h出现白色固体,继续通HC1气体2.5h,停止反应,将反应容器密封放置24h。典型的实验方法即在三颈烧瓶中加入多聚甲醛1.6g，无水氯化锌4.0g和浓盐酸6mL,加热搅拌,当温度升至60℃时,加入烷基苯0.2mol,并迅速通入由浓硫酸和氯化钠反应产生的干燥氯化氢气体,通过浓硫酸的滴加速度控制通入气体的量,多余气体用水吸收.反应6h后结束,冷却后于分液漏斗中分液,有机层依次用10%碳酸钠水溶液洗涤2次、蒸馏水洗涤3次,然后用无水硫酸钠干燥,过滤,蒸除多余的烷基苯,最后减压蒸馏得到烷基苄氯,称重计算收率.Ina2-l.round-bottomedflask,equippedwithasealedmechanicalstirrer(Note1),agasinlettube,andarefluxcondenser,areplaced200g.(1.66moles)ofmesitylene,1l.ofconcentratedhydrochloricacid,and63ml.(0.84mole)offormaldehydesolution(concentration,37%)(Note2).Hydrogenchlorideisintroducedbelowthesurfaceofthemixture(Note3),whichisstirredvigorouslyandheatedinawaterbathkeptat 55.Theseconditionsaremaintainedthroughoutthereaction,whichrequiresatotalof5.5hours.Atthehalfwaypoint,anadditional63ml.(0.84mole)offormaldehydesolutionisadded(Note4).Organicsyntheses在氯甲基化反应过程中，多聚甲醛的溶解是很重要的，它直接影响着产品的质量和收率，因邻二甲氧基苯之前用盐酸将多聚甲醛充分溶解。经多次试验在40～45℃保温1小时即可全溶。全溶后多聚甲醛以甲醛分子状态存在，当加入邻二甲氧基苯的氯仿溶液时，氯甲基化反应即开始，经试验该反应在28～30℃约需5小时反应完成。反应温度不能太高，否则3，4一二甲氧基氯苄将分解并有副产物形成。4,6-二甲基一1,3一二(溴甲基)苯的合成250mL三颈瓶中加入多聚甲醛4.5g(0.15mol)、溴化钠18.1g(0.17mol)、间二甲苯9．2mL(0.075mol)及冰醋酸78mL。将36mL浓硫酸与等体积冰醋酸配制成混合液，剧烈搅拌下缓慢滴加到三颈瓶中，升温至80～85℃，反应4～6h。冷却至室温，溶液倾倒人400mL水中，析出白色絮状固体，抽滤，水洗至中性．烘箱(30～35℃)干燥。62%