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• 2018-12-08 14:51發(fā)布了問(wèn)答

  藥物過(guò)敏怎么辦 黃胺類藥物過(guò)敏怎么辦

  　

  461人看過(guò)

• 2018-11-28 15:45發(fā)布了問(wèn)答

  消膽胺的消膽胺

  　

  310人看過(guò)

• 2017-09-09 08:00發(fā)布了問(wèn)答

  降壓藥苯磺酸氨氯地平片一天吃四分之一顆還有用嗎?

  去年4月份得了心肌炎，后來(lái)一直服藥到12月底時(shí)復(fù)查說(shuō)心肌炎癥狀沒(méi)有了，但是血壓高，做過(guò)動(dòng)態(tài)血壓，醫(yī)生說(shuō)患了高血壓，一直服用苯磺酸氨氯地平片，現(xiàn)在已經(jīng)一天只服用四分之一片，血壓基本維持在100-110/60-75，請(qǐng)問(wèn)可以停藥嗎？

  1843人看過(guò)

• 2017-04-26 00:33發(fā)布了問(wèn)答

  洋河封藏大典上提到的“三老、兩多、數(shù)量少”是什么意思？

  　

  477人看過(guò)

• 2017-03-26 12:18發(fā)布了問(wèn)答

  醚類，酮類有哪些物理和化學(xué)性質(zhì)

  　

  558人看過(guò)

• 2017-02-23 17:55發(fā)布了問(wèn)答

  褪黑素能與歸脾顆粒一起吃嗎

  　

  735人看過(guò)

• 2016-10-22 11:09發(fā)布了問(wèn)答

  洗衣液，aes，磺酸，體系可以用椰油酸鉀皂嗎

  　

  479人看過(guò)

• 2016-09-25 22:26發(fā)布了問(wèn)答

  灌封膠的區(qū)別

  　

  432人看過(guò)

• 2015-12-23 21:17發(fā)布了問(wèn)答

  一周三根煙危害大嗎

  　

  727人看過(guò)

• 2012-11-22 12:57發(fā)布了問(wèn)答

  腈基和羥基生成的化合物是什么

  　

  464人看過(guò)

• 2012-08-31 01:19發(fā)布了問(wèn)答

  文獻(xiàn)求翻譯

  Since the formation of a titanacyclopropane en route to cyclopropylamines can only occur with alkylmagnesium halides that contain a b-hydrogen atom， Grignard reagents without b-hydrogens appeared to be the most promising reagents for th... Since the formation of a titanacyclopropane en route to cyclopropylamines can only occur with alkylmagnesium halides that contain a b-hydrogen atom， Grignard reagents without b-hydrogens appeared to be the most promising reagents for the synthesis of primary tert-alkylamines from nitriles (Scheme 1). Thus propionitrile (1a)， phenylmagnesium bromide (2) and Ti(Oi-Pr)4 were chosen to optimize the reaction conditions. In the protocol for the synthesis of cyclopropylamines，10 Ti(Oi-Pr)4 is already present in the diethyl ether solution of a nitrile， before two equivalents of the Grignard reagent are added. As this did not appear to be optimal for the synthesis of primary tertalkylamines， the Grignard reagent was added before Ti(Oi-Pr)4. With 2 equivalents of PhMgBr， 0.1 equivalent of Ti(Oi-Pr)4， and 1 equivalent of propionitrile (1a)， the primary tert-alkylamine 8a was not formed at all. With an equimolar quantity of Ti(Oi-Pr)4， the amine 8a was produced in a low yield (11%) but with 1 equivalent of Ti(Oi- Pr)4 and 3 equivalents of the Grignard reagent 2， a 60% yield of 8a was obtained. Monitoring of the reaction by workup of aliquots of the reaction mixture showed that the first addition of 2 to form the N-magnesio derivative of the corresponding imine was rapid， whereas the subsequent second addition of the Grignard reagent 2 required heating under reflux for up to 24 hours. In tetrahydrofuran instead of diethyl ether， the amine 8a was formed in a very low yield， if at all. 展開

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• 2007-07-23 01:05發(fā)布了問(wèn)答

  何謂----美拉德反應(yīng)？

  　

  466人看過(guò)

• 2007-03-31 05:28發(fā)布了問(wèn)答

  α-脫羧是什么意思

  　

  912人看過(guò)