质谱中反偶电子规则并含双电荷离子的两类联苯化合物的裂解机理
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摘要
利用气相色谱-质谱法分别对含C≡C桥键、CF_2O桥键及双CF_2O桥键的联苯类化合物进行分析,在各个化合物的谱图中均存在显著的奇电子自由基离子峰(反偶电子规则)和双电荷碎片离子峰.根据所得实验结果,归纳以上化合物中奇电子离子的生成途径分别为:(1)游离基中心诱导苄基C_(sp~3)—C_(sp~3)键均裂后再经另一苄基C_(sp~3)—C_(sp~3)键均裂,即α-σ裂解;(2)电荷中心静电诱导C_(sp~3)—O_(sp~3)键异裂后再经苄基C_(sp~3)—C_(sp~3)键或C_(sp~3)—O_(sp~3)键均裂,即i-σ裂解.推测引起σ键裂解的机制是由内转换引起的.双电荷离子的生成受2个相互独立官能团上既含游离基又含电荷的活化反应中心共同诱导控制裂解得到,生成途径分别为:(1)2个相互独立的游离基中心分别诱导苄基C_(sp~3)—C_(sp~3)键双均裂得到,即αα双重控制裂解反应;(2)独立的游离基中心诱导C_(sp~3)—C_(sp~3)均裂及另一电荷中心静电诱导C_(sp~3)—O_(sp~3)键异裂得到,即iα双重控制裂解反应;(3)2个相互独立的电荷中心分别静电诱导C_(sp~3)—O_(sp~3)键双异裂,即ii双重控制裂解反应.采用密度泛函理论(DFT)方法对具有代表性的化合物的裂解途径进行了初步计算,结果与前述裂解机制一致.
The formation of odd electron ion(OE+·) by cleavage of even electron ion(EE+) is an anomalous reaction violates the"even-electron rule".Two kinds of liquid crystal compounds,which have the structures of biphenyl with C≡C or CF_2O moiety as a linkage group,were analyzed by gas chromatography-mass spectrometer(GC-MS).The results show that the spectra of the compounds are obtained by remarkable odd electron radical ion peaks and doubly charged fragment ion peaks,so the cleavage pathways were similar for the two kinds of compounds.We noted a sequential loss of alkyl,alkyl,or phenoxyl radicals under electron impact,which seems to be frequent in the case of liquid crystal compounds.The achievement of a higher degree of aromaticity may be the driving force for these processes.For the alkyl biphenyl compounds with C ≡C central-bridge-bond,the cleavage of the alkyl carbon-carbon bond is initiated by the loss of alkyl radical via the α-cleavage,followed by the the losing of the other alkyl radical by σ bond cleavage,i.e.,α-σcleavage.For the alkyl biphenyl compounds with CF_2O central-bridge-bond,the cleavage of the carbon-oxygen bond is initiated by the loss of phenoxyl radical via the i-cleavage,followed by the losing of the other alkyl radical by σ bond cleavage,i.e.,i-σ cleavage.For the biphenyl compounds with double CF_2O central-bridge-bond,the cleavage of the carbon-oxygen bond is initiated by the loss of phenoxyl radical via the i-cleavage,followed by the losing of the other phenoxyl radical by σ-bond cleavage,i.e.,i-σ cleavage.The obtained results suggest the reason of σ-bond breakage,which should be caused by an internal conversion(IC).Generally,doubly charged ions are found in the electron ionization(EI) mass spectra of hydrocarbons,but the intensities of them are weak and cannot be used in chemical analyses.In contrast,in this paper we showed two kinds of liquid crystal compounds,as interesting examples,which can eliminate two internal alkyl or phenoxyl groups as radicals and yield the most abundant doubly charged ions in their EI mass spectrum by αα/iα or ii cleavage reactions.As an example,the DFT method is adopted to simulating the cleavage pathway of compound 2 d.A conclusion can be draw that the proposed fragmentation mechanism is agreed by both experimental data and theoretical research.
The formation of odd electron ion(OE+·) by cleavage of even electron ion(EE+) is an anomalous reaction violates the"even-electron rule".Two kinds of liquid crystal compounds,which have the structures of biphenyl with C≡C or CF_2O moiety as a linkage group,were analyzed by gas chromatography-mass spectrometer(GC-MS).The results show that the spectra of the compounds are obtained by remarkable odd electron radical ion peaks and doubly charged fragment ion peaks,so the cleavage pathways were similar for the two kinds of compounds.We noted a sequential loss of alkyl,alkyl,or phenoxyl radicals under electron impact,which seems to be frequent in the case of liquid crystal compounds.The achievement of a higher degree of aromaticity may be the driving force for these processes.For the alkyl biphenyl compounds with C ≡C central-bridge-bond,the cleavage of the alkyl carbon-carbon bond is initiated by the loss of alkyl radical via the α-cleavage,followed by the the losing of the other alkyl radical by σ bond cleavage,i.e.,α-σcleavage.For the alkyl biphenyl compounds with CF_2O central-bridge-bond,the cleavage of the carbon-oxygen bond is initiated by the loss of phenoxyl radical via the i-cleavage,followed by the losing of the other alkyl radical by σ bond cleavage,i.e.,i-σ cleavage.For the biphenyl compounds with double CF_2O central-bridge-bond,the cleavage of the carbon-oxygen bond is initiated by the loss of phenoxyl radical via the i-cleavage,followed by the losing of the other phenoxyl radical by σ-bond cleavage,i.e.,i-σ cleavage.The obtained results suggest the reason of σ-bond breakage,which should be caused by an internal conversion(IC).Generally,doubly charged ions are found in the electron ionization(EI) mass spectra of hydrocarbons,but the intensities of them are weak and cannot be used in chemical analyses.In contrast,in this paper we showed two kinds of liquid crystal compounds,as interesting examples,which can eliminate two internal alkyl or phenoxyl groups as radicals and yield the most abundant doubly charged ions in their EI mass spectrum by αα/iα or ii cleavage reactions.As an example,the DFT method is adopted to simulating the cleavage pathway of compound 2 d.A conclusion can be draw that the proposed fragmentation mechanism is agreed by both experimental data and theoretical research.
引文
[1]Mathur B.P.,Abbey L.E.,Burgess E.M.,Moran T.F.,Org.Mass Spectrom.,1980,15(6),312—316
[2]Mathur B.P.,Burgess E.M.,Bostwick D.E.,Moran T.F.,Org.Mass Spectrom.,1981,16(1),92—96
[3]Jones B.E.,Abbey L.E.,Chatham H.L.,Hanner A.W.,Teleshfsky L.A.,Burgess E.M.,Moran T.F.,Org.Mass Spectrom.,1982,17(1),10—18
[4]Hanner A.W.,Abbey L.E.,Bostwick D.E.,Burgess E.M.,Moran T.F.,Org.Mass Spectrom.,1982,17(1),19—28
[5]Teleshefsky L.A.,Jones B.E.,Abbey L.E.,Bostwick D.E.,Burgess E.M.,Moran T.F.,Org.Mass Spectrom.,1982,17(106),481—492
[6]Appling J.R.,Jones B.E.,Abbey L.E.,Bostwick D.E.,Moran T.F.,Org.Mass Spectrom.,1983,18(7),282—294
[7]Appling J.R.,Musier K.M.,Moran T.F.,Org.Mass Spectrom.,1984,19(9),412—422
[8]Appling J.R.,Burdick G.W.,Moran T.F.,Org.Mass Spectrom.,1985,20(5),343—350
[9]Shamma M.,Dudock B.S.,Cava M.P.,Rao K.V.,Dalton D.R.,Dejongh D.C.,Shrader S.R.,Chem.Commun.,1966,1(1),7—8
[10]Mc Lafferty F.,Tureˇcek F.,Interpretation of Mass Spectra,University Science Books,California,1993,115—116
[11]Gross J.H.,Mass Spectrometry,Science Press,Beijing,2012,257—259
[12]Karni M.,Mandelbaum A.,Org.Mass Spectrom.,1980,15(2),53—64
[13]Bowen R.D.,Harrison A.G.,Org.Mass Spectrom.,1981,16(16),180—182
[14]Ceraulo L.,Agozzino P.,Ferrugia M.,Lamartina L.,Natoli M.C.,Org.Mass Spectrom.,1991,26(4),279—286
[15]Attygalle A.B.,Bialecki J.B.,Nishshanka U.,Weisbecker C.S.,Ruzicka J.,J.Mass Spectrom.,2008,43(9),1224—1234
[16]Vessecchi R.,Carollo C.A.,Lopes J.N.C.,Crotti A.E.M.,Lopes N.P.,Galembeck S.E.,J.Mass Spectrom.,2009,44(8),1224—1233
[17]Cai Y.,Mo Z.,Rannulu N.S.,Guan B.,Kannupal S.,Gibb B.C.,Cole R.B.,J.Mass Spectrom.,2010,45(3),235—240
[18]Chai Y.F.,Gan S.F.,Pan Y.J.,Acta Chim.Sinica,2012,70(17),1805—1811(柴云峰,甘世凤,潘远江.化学学报,2012,70(17),1805—1811)
[19]Nizigiyimana L.,Rajan P.K.,Haemers A.,Claeys M.,Derrick P.J.,Rapid Commun.Mass Spectrom.,1997,11(16),1808—1812
[20]Ji H.Y.,Synthesis and Properties of Novel Polyaryls,East China Normal University,Shanghai,2009(冀海英.新型联芳共轭有机化合物的合成及其性能研究,上海:华东师范大学,2009)
[21]Gao A.A.,Zheng Y.Y.,Du W.S.,Chinese Journal of Liquid Crystals and Displays,2014,29(2),159—171(高嫒嫒,郑远洋,杜渭松.液晶与显示,2014,29(2),159—171)
[22]Meng F.B.,Lian J.,Gao Y.M.,Progress in Chemistry,2008,20(4),499—507(孟凡宝,廉娇,高永梅.化学进展,2008,20(4),499—507)
[23]Gao H.J.,Liquid Crystal Chemistry,Tsinghua University Press,Beijing,2011(高鸿锦.液晶化学,北京:清华大学出版社,2011)
[24]Liu Y.,Zhang Z.Y.,Ren Z.D.,Chinese Journal of Liquid Crystals and Displays,2010,25(4),490—493(刘运,张智勇,任占冬.液晶与显示,2010,25(4),490—493)
[25]Zhang F.M.,Han Y.H.,Shang H.Y.,Chinese Journal of Liquid Crystals and Displays,2010,25(4),510—514(张芳苗,韩耀华,尚洪勇.液晶与显示,2010,25(4),510—514)
[26]Wang Y.,Li M.,Journal of Chinese Mass Spectrometry Society,2015,36(3),255—260(王毅,李敏.质谱学报,2015,36(3),255—260)
[27]Wang Y.,Zhang P.,Wu S.X.,Chinese Journal of Liquid Crystals and Displays,2016,31(11),1046—1054(王毅,张苹,吴生秀.液晶与显示,2016,31(11),1046—1054)
[28]Wang C.H.,Techniques and Methods in Organic Mass Spectrometry,China Light Industry Press,Beijing,2011(王聪慧.有机质谱技术与方法,北京:中国轻工业出版社,2011)
[29]Alex A.,Harvey S.,Parsons T.,Pullen F.S.,Wright P.,Riley J.A.,Rapid Commun.Mass Spectrom.,2009,23(17),2619—2627
[2]Mathur B.P.,Burgess E.M.,Bostwick D.E.,Moran T.F.,Org.Mass Spectrom.,1981,16(1),92—96
[3]Jones B.E.,Abbey L.E.,Chatham H.L.,Hanner A.W.,Teleshfsky L.A.,Burgess E.M.,Moran T.F.,Org.Mass Spectrom.,1982,17(1),10—18
[4]Hanner A.W.,Abbey L.E.,Bostwick D.E.,Burgess E.M.,Moran T.F.,Org.Mass Spectrom.,1982,17(1),19—28
[5]Teleshefsky L.A.,Jones B.E.,Abbey L.E.,Bostwick D.E.,Burgess E.M.,Moran T.F.,Org.Mass Spectrom.,1982,17(106),481—492
[6]Appling J.R.,Jones B.E.,Abbey L.E.,Bostwick D.E.,Moran T.F.,Org.Mass Spectrom.,1983,18(7),282—294
[7]Appling J.R.,Musier K.M.,Moran T.F.,Org.Mass Spectrom.,1984,19(9),412—422
[8]Appling J.R.,Burdick G.W.,Moran T.F.,Org.Mass Spectrom.,1985,20(5),343—350
[9]Shamma M.,Dudock B.S.,Cava M.P.,Rao K.V.,Dalton D.R.,Dejongh D.C.,Shrader S.R.,Chem.Commun.,1966,1(1),7—8
[10]Mc Lafferty F.,Tureˇcek F.,Interpretation of Mass Spectra,University Science Books,California,1993,115—116
[11]Gross J.H.,Mass Spectrometry,Science Press,Beijing,2012,257—259
[12]Karni M.,Mandelbaum A.,Org.Mass Spectrom.,1980,15(2),53—64
[13]Bowen R.D.,Harrison A.G.,Org.Mass Spectrom.,1981,16(16),180—182
[14]Ceraulo L.,Agozzino P.,Ferrugia M.,Lamartina L.,Natoli M.C.,Org.Mass Spectrom.,1991,26(4),279—286
[15]Attygalle A.B.,Bialecki J.B.,Nishshanka U.,Weisbecker C.S.,Ruzicka J.,J.Mass Spectrom.,2008,43(9),1224—1234
[16]Vessecchi R.,Carollo C.A.,Lopes J.N.C.,Crotti A.E.M.,Lopes N.P.,Galembeck S.E.,J.Mass Spectrom.,2009,44(8),1224—1233
[17]Cai Y.,Mo Z.,Rannulu N.S.,Guan B.,Kannupal S.,Gibb B.C.,Cole R.B.,J.Mass Spectrom.,2010,45(3),235—240
[18]Chai Y.F.,Gan S.F.,Pan Y.J.,Acta Chim.Sinica,2012,70(17),1805—1811(柴云峰,甘世凤,潘远江.化学学报,2012,70(17),1805—1811)
[19]Nizigiyimana L.,Rajan P.K.,Haemers A.,Claeys M.,Derrick P.J.,Rapid Commun.Mass Spectrom.,1997,11(16),1808—1812
[20]Ji H.Y.,Synthesis and Properties of Novel Polyaryls,East China Normal University,Shanghai,2009(冀海英.新型联芳共轭有机化合物的合成及其性能研究,上海:华东师范大学,2009)
[21]Gao A.A.,Zheng Y.Y.,Du W.S.,Chinese Journal of Liquid Crystals and Displays,2014,29(2),159—171(高嫒嫒,郑远洋,杜渭松.液晶与显示,2014,29(2),159—171)
[22]Meng F.B.,Lian J.,Gao Y.M.,Progress in Chemistry,2008,20(4),499—507(孟凡宝,廉娇,高永梅.化学进展,2008,20(4),499—507)
[23]Gao H.J.,Liquid Crystal Chemistry,Tsinghua University Press,Beijing,2011(高鸿锦.液晶化学,北京:清华大学出版社,2011)
[24]Liu Y.,Zhang Z.Y.,Ren Z.D.,Chinese Journal of Liquid Crystals and Displays,2010,25(4),490—493(刘运,张智勇,任占冬.液晶与显示,2010,25(4),490—493)
[25]Zhang F.M.,Han Y.H.,Shang H.Y.,Chinese Journal of Liquid Crystals and Displays,2010,25(4),510—514(张芳苗,韩耀华,尚洪勇.液晶与显示,2010,25(4),510—514)
[26]Wang Y.,Li M.,Journal of Chinese Mass Spectrometry Society,2015,36(3),255—260(王毅,李敏.质谱学报,2015,36(3),255—260)
[27]Wang Y.,Zhang P.,Wu S.X.,Chinese Journal of Liquid Crystals and Displays,2016,31(11),1046—1054(王毅,张苹,吴生秀.液晶与显示,2016,31(11),1046—1054)
[28]Wang C.H.,Techniques and Methods in Organic Mass Spectrometry,China Light Industry Press,Beijing,2011(王聪慧.有机质谱技术与方法,北京:中国轻工业出版社,2011)
[29]Alex A.,Harvey S.,Parsons T.,Pullen F.S.,Wright P.,Riley J.A.,Rapid Commun.Mass Spectrom.,2009,23(17),2619—2627