【正文】 Vol. I, p. 269.[10] M. S. Kharasch, G. Stampa, V. Kutlenburg, J .Oig. Pheni , 18,575 (1953)[11] 11. S. Rharasch, F. L. Lambert, W. H. Urry, J .Oig. rhein., 10, 298 (1945).。該少量氣體（25mL)收集和分析方法如前所述，結(jié)果列于表2中。4—苯氧基丁基溴由卡?瑞斯克法制備。b， 、1g溴化鈷加于15mL乙醚中，并與其中緩慢的加入1M的甲基溴化鎂25mL。反應(yīng)氣體收集分析如前。在二甲苯和丁醚中，格式試劑是通過一以漿狀的形態(tài)加入，產(chǎn)生氣體的收集和分析方式如前所述。所用的溶劑分別為乙醚、丁醚、二甲苯。不同溶劑中1,4—二溴丁烷和甲基溴化鎂與溴化鈷的反應(yīng)。相關(guān)氣體的測定、分析通過上訴過程來完成。（）的1,4—二溴丁烷，回流。每種化合物的摩爾百分?jǐn)?shù)是通過下面的式子計算而來：儀器：帶有地液漏斗和冷凝裝置的100mL三口燒瓶，磁力攪拌器，氣體收集裝置。（圖 1 ）。洗脫氣體是氦氣。氣體催化方法。正溴丁烷通過托德列蒸餾法蒸餾。丁醚通過稀氫氧化鉀溶液和水洗滌。實驗試劑：1,4—二溴丁烷（通過威德默分餾柱仔細(xì)的蒸餾過）。這些因素在決定反應(yīng)產(chǎn)物的產(chǎn)量上毫無疑問起著重要作用。雖然這種異構(gòu)化反應(yīng)在較低溫度下進行時有這樣一種可能性，不過很然有一種可能即在反應(yīng)釜中于丁醚和二甲苯回流下，1—丁烯有足夠長的停留時間來進行如此一個重排反應(yīng)。這表明甲基和丁基自由基的重組反應(yīng)是一個比任何生成2—丁烯的反應(yīng)都快的反應(yīng)。在另一實驗中我們將丁基溴和溴化鈷與甲基溴化鎂進行反應(yīng)，在該反應(yīng)條件下，我們未發(fā)現(xiàn)在產(chǎn)物中有2—丁烯生成（表 2 ）。他們提出的關(guān)于正丁基自由基通過氫原子的遷移而生成2—丁基自由基的重排反應(yīng)沒有能夠得到實驗的進一步支持。另一個主要的產(chǎn)物是戊烷（63%）在上述研究的反應(yīng)中都有順式2—丁烯和反式2—二丁烯生成（順式和反式摩爾比從兩倍到五倍之間變化）?？?瑞斯克，斯坦帕和能丁本格[10]報道說4—苯氧基丁基溴，鎂和溴化鈷在乙醚中反應(yīng)主要生成丁基苯基醚和丁烯基苯基醚。對這一混合物的分析顯示：所得到的產(chǎn)物與在1,4—二溴丁烷反應(yīng)中所制得的產(chǎn)物是一致的。為了檢驗反應(yīng)中間體是4—溴—1—丁基自由基（Ａ）這一假說，我們在二甲苯溶液中進行了通過鎂與溴化鈷催化回流分解4—苯氧基丁基溴的反應(yīng)。關(guān)于活潑基團置換反應(yīng)的實驗證據(jù)已經(jīng)被斯特西總結(jié)過了。4—溴—1—丁基自由基（A）可以由生成的金屬鹵化物直接制的或者由中間態(tài)的金屬烷基熱分解生成[8]。然而，應(yīng)當(dāng)記住，對于任何像上述這些復(fù)雜的反應(yīng)，雖然對反應(yīng)機理尋找到一個合理的解釋并不是很困難的，但是只有在眾多解釋中懸著一種最為合理的解釋才是最好的。這系類反應(yīng)的結(jié)果也別列在了表 1 中，在較低溫度的乙醚溶液中回流時，沒有環(huán)丁烷生成——這是對卡森和韋[3]實驗結(jié)果觀察的一個意想不到的結(jié)果。他們提出了自由基反應(yīng)式通過下面的歷程來進行的。為了進一步從本質(zhì)上區(qū)分該脫鹵反應(yīng)是自由基反應(yīng)還是離子反應(yīng)，在更傾向于自由基反應(yīng)條件下我們重新進行了一下該反應(yīng)。表 1 1,4—二溴丁烷的脫鹵反應(yīng)（）反應(yīng)試劑溶劑總產(chǎn)量收率/%（mol）乙烯丁烷1—丁烯Na二甲苯8063165Li二甲苯90164615Mg二甲苯90145112Na丁醚a200High..Mg丁醚a190312419Zn丁醚a260342816Zn二氧雜環(huán)乙烷60274713Mg+CoBr2丁醚a20082416Mg+CoBr2乙醚7083342CH3MgBr+CoBr2二甲苯b…c2138CH3MgBr+CoBr2丁醚…c231715CH3MgBr+CoBr2乙醚…c6351反應(yīng)試劑溶劑總產(chǎn)量收率/%（mol）2—丁烯1,3—丁二烯環(huán)丁烷Na二甲苯802311Li二甲苯905513Mg二甲苯904613Na丁醚a200..0Mg丁醚a190629Zn丁醚a2601110Zn二氧雜環(huán)乙烷601300Mg+CoBr2丁醚a2001331Mg+CoBr2乙醚701700CH3MgBr+CoBr2二甲苯b…c542CH3MgBr+CoBr2丁醚…c3008CH3MgBr+CoBr2乙醚…c1700a：產(chǎn)物在在丁基醚的高產(chǎn)量是由于金屬與溶劑的副反應(yīng) ；其它的產(chǎn)物是丙烷，.；b:此外，發(fā)現(xiàn)了53%的乙烷和4%的丙烷；c:沒有測得反應(yīng)產(chǎn)物的收率是因為此處被稀釋于大量的甲烷中。沸騰的丁醚與鈉反應(yīng)會生成較大數(shù)量的丙烷和較少量的碳—3和碳—4碳?xì)浠衔铩υ摲磻?yīng)生成的混合物的分析是通過氣相色層分析法來完成的（圖1）。他們提出了初步的有機鋅鹵化物的形成機理以及隨后的該有機鋅鹵化物被離子解離的過程。然而哈莫尼特[5]在相同的條件下制得了丁烷。盡管他們沒有能夠提出該反應(yīng)的機理，然而通過對環(huán)丁烷在較少的苯沸騰溶液中生成過程的進一步觀察解釋了該過程是一個反應(yīng)活性較高的反應(yīng)。這兩位作者對此反應(yīng)提出的反應(yīng)機理包括1,4—丁基自由基的生成以及該自由基隨后生成前面提到的產(chǎn)物的相關(guān)反應(yīng)。本文就是對此類研究的一個相關(guān)報道。通過對1,4—二溴丁烷的金屬脫鹵反應(yīng)的文獻的大量查閱，筆者發(fā)現(xiàn)對已報道的產(chǎn)物各自的反應(yīng)機理之間存在著很大的差異。 Vol. I, p. 269.[10] M. S. Kharasch, G. Stampa, V. Kutlenburg, J .Oig. Pheni , 18,575 (1953)[11] 11. S. Rharasch, F. L. Lambert, W. H. Urry, J .Oig. rhein., 10, 298 (1945).1,4—二溴丁烷的一些脫鹵反應(yīng)[1]WILLIAM B. SMITH對于脫鹵反應(yīng)，已經(jīng)發(fā)現(xiàn)在一系列的條件下1,4—二溴丁烷可以脫鹵生成丁烷，1—丁烯，順式2 —丁烯，反式2—丁烯，環(huán)丁烷和1,3—丁二烯的混合物。 in a gas collection bottle filled either with mercury or a saturated salt solution.Reaction of 1,4dibromobutane with, various metals. To a refluxing mixture of 2 g. of the appropriate metal and 20 ml of solvent was slowly added g. ( mole) of 1,4dibromobutane. The mixture was usually allowed to reflux overnight. The evolved gases were then measured and analyzed according to the above procedure. The metals, solvents, and reaction products are tabulated in Table I.Reaction of 1,4dibromobutane with methylmagnesium bromide and cobaltous bromide in various solvents. To a refluxing mixture of g. ( mole) of 1,4dibromobutane and 2 g. of cobaltous bromide in 20 ml. of solvent, was added ca. mole of methylmagnesium bromide in the same solvent. The solvents used were ethyl ether, butyl ether, and xylene. In the latter two solvents, the addition reagent was formed by mixing the solvent with the appropriate amount of methylmagnesium bromide in ethyl ether and then removing as much of the ethyl ether as possible by evacuating to water pump pressure. In xylene and butyl ether, the Grignard reagent was added in the form of a slurry. The gases produced were collected and analyzed as described previously.Reactions of nbutyl bromide. (a) A mixture of g. of nbutyl bromide ( mole), g. of cobaltous bromide ( mole), and 1 g. of magnesium was refluxed in 15 ml. of ethyl ether for three hours. The reaction gas was collected and analyzed as before. The results are recorded in Table II.(b) To a refluxing mixture of g. of nbutyl bromide and 1 g. of cobaltous bromide in 15 ml. of ethyl ether was slowly added 25 ml. of ca. 1M rnethylmagnesium bromide. The yield of gas was quantitative based on the amount of methylmagnesium bromide. The analytical results are given in Table II.Reaction of 4phenoxybutyl bromide with magnesium and cobaltous bromide. 4Phenoxybutyl bromide was prepared by the method of Kharasch, et al.。 . 176。 . 141176。 the other product being propane. Small amount is abbreviated . b In addition, 53% ethane and 4% propane were found. C No yield of reaction products was measured here due to the large dilution by methane.The experimental results of this study support the view that the metal dehalogenation reactions of 1,4dibromobutane are free radical in nature. However, it should be born in mind that in any reactions as plex as these there is no difficulty in finding explanations of the experimental facts, but only in defending a preferred explanation selected from many. One reasonable reaction scheme which will acmodate the above observations is as follows:In the same fashion the 4bromolbutene (Equation 4) may depose to form 1,3butadiene and 1butene. The 4bromolbutyl radical (A) may be generated either by the direct abstraction of the halogen by the metal or by the thermal deposition of a metal alkyl intermediate.[8]The formation of cyclobutane as envisioned in Equation 2 above is a displacement of bromine atom from carbon by an attacking radical. The expe