heappearanceofthe1HNMRsignalsofproticsamplesinaproticsolventsdependscriticallyontheconcentrationofthesample.The-OH,-NH2or-COOHsignalscanhavechemicalshiftvaluesandlinewidthsoverawiderangeduetovaryingextentsofhydrogenbondingandchemicalexchange.TheconcentrationcanalsodeterminewhetherornotoneisabletoobserveJcouplingbetweenand-OHprotonandotherprotonsinthesample.Anexampleofthisisillustratedbelow.Thefigu...[
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NMRusersareveryfamiliarwiththeadvantagesofprotondecouplingwhenobserving13C.The13CNMRspectraofphosphoruscontainingcompoundscanbemadesimplerbyapplying31Pdecouplingeitheronitsownorinadditiontoprotondecoupling.Thefigurebelowshowsthe13CNMRspectrumofdimethylmethylphosphonatewithallpossiblecombinationsofprotonand31Pdecoupling.Thedatacollectionrequiredatripleresonanceprobewiththeappropriatebandpassfilters...[
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【英文名称】DibutyltinOxide【分子式】C8H18OSn【分子量】248.92【CA登录号】[818-08-6]【缩写和别名】DBTO【结构式】(CH3CH2CH2CH2)2SnO【物理性质】mp>300oC，溶于大多数有机溶剂，常常在苯、甲苯或者CH3OH溶液中使用。【制备和商品】该试剂在国外大型化学试剂公司有销售。由于具有较高的毒性，建议不要在实验室制备。【注意事项】该试剂由于具有C-Sn键而具有较高的毒性，建议在通风[
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本维莫德是一种小分子芪类化合物，最初是由一种土壤线虫共生菌的代谢产物中分离得到，属于天然产物的范畴，目前完全可以通过人工合成获得；同时也是全球首个芳香烃受体激动剂。2019年5月在我国获批上市；2022年5月在美国获批上市。本维莫德是我国近十年(2012年到2022年)批准上市的三款firstinclass创新药之一，也是目前为止首款先在我国批准上市，然后才被美国FDA批准上市[
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常用的酚羟基保护基有：（1）烷基保护基，比如甲基，叔丁基或三苯基甲基；（2）苄基类保护基，比如Bn或者PMB；（3）烯丙基；（4）硅类保护基，比如TBS；（5）酰基保护基，比如乙酰基或苯甲酰基；（6）MOM保护基；（7）THP保护基；（8）SEM保护基；（9）二甲胺磺酰基；（10）烷氧羰基等等。酚羟基各类保护基如何脱保护。总体来说可以分为如下：（1）酸脱保护，上图中的例[
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Whenmanychemistsareaskedwhatisthe2JH-Hcouplingforcompoundslikemethane,acetone,methylenechloride,dimethyletherorDMSO,theywilloftenreturnalookofconfusion."Thereisnocoupling,"theywillsay,"theprotonspectrumisasinglet".Indeedtheprotonspectrumisasingletforthesecompoundsbut2JH-Hisnotequaltozero.Theonlyreasonthatthecouplingisnotobservedinthespectrumisbecausethechemicalshiftsofeachproto...[
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Manypeopleusestatementslike,"ItisfastontheNMRtimescale"withoutreallyhavinganunderstandingofwhatthe"NMRtimescale"means.Assumewehaveacompoundwithtwointer-convertibleconformations,AandB,eachofwhichgivesadifferentNMRspectrum.IftheinterconversionbetweenAandBisveryslowthenweexpecttogetaspectrumwithbothconformationsAandBresolved.Iftheinterconversionisveryfastthenwewouldgetanunresolved...[
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ItisveryimportantthatyourNMRsamplesaremixedwellbeforeNMRdataareacquired.Ifthesamplehasaconcentrationgradient(i.e.moreconcentratedatoneendofthesamplecolumncomparedtotheother)itwillbeverydifficulttoshimthemagnetovertheentirevolumeofthesampleasthemagneticsusceptibilityisnotconstantoverthesamplevolume.AsaresulttheNMRlinesmaybeskewedandwillbemuchbroaderthannecessary.Thiswillleadtoamuchlowersignal-to-no...[
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二乙氨基三氟化硫(DAST)是有机合成中被广泛应用的氟化试剂，它是(二烃基氨基)三氟化硫家族中的一个成员。DAST属于亲核型氟化试剂，它能够将醇羟基转化成为相应的氟，将醛酮转化成为偕二氟化物[1]。DAST将伯醇转化成为相应氟化物的反应可以在非常温和的条件下进行。通常在–78oC下加料来抑制最初的放热过程，然后让反应自动升至室温片刻即可(式1)[2,3]。仲醇的反应虽然[
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