Boc是可以说是氨基最常用的保护基了，好上又好脱。我们知道Boc最常用的方法是酸性条件脱保护，像三氟乙酸，盐酸，甲酸，对甲苯磺酸等等。用二氯甲烷作溶剂，加三氟乙酸搅拌搅拌很容易脱除Boc；或者企业界用的比较多的氯化氢二氧六环溶液等等。 使用氯化氢溶液脱Boc的时候，含有氧杂环丁烷（TrimethyleneOxide）和氮杂环丁烷（Azetidine）结构的底物进行脱Boc的时候，就存[阅读全文]
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(2023-03-12 09:44:12)
Boc是可以说是氨基最常用的保护基了，好上又好脱。我们知道Boc最常用的方法是酸性条件脱保护，像三氟乙酸，盐酸，甲酸，对甲苯磺酸等等。用二氯甲烷作溶剂，加三氟乙酸搅拌搅拌很容易脱除Boc；或者企业界用的比较多的氯化氢二氧六环溶液等等。 使用氯化氢溶液脱Boc的时候，含有氧杂环丁烷（TrimethyleneOxide）和氮杂环丁烷（Azetidine）结构的底物进行脱Boc的时候，就存[阅读全文]
(2023-03-12 09:22:54)
【英文名称】NitrosoniumTetrafluoroborate 【分子式】NOBF4 【分子量】116.82 【CAS号】14635-75-7 【缩写和别名】NitrosylTetrafluoroborate 【物理性质】无色结晶状固体,mp250℃(升华)，d2.185g/cm³，溶于乙腈溶剂中。 【制备和商品】国际大型试剂公司有销售。 【注意事项】容易潮解，须在无水条件下使用和储存。 四氟硼酸亚硝是一种温和的单电子转移氧化剂，NO/NO?在乙睛[阅读全文]
(2023-03-12 09:06:23)
TBAF释放的氟离子可与硅原子形成稳定的Si-F键，广泛应用于去硅烷基反应，这类反应通常可以在比较温和的条件下进行，且产率很高，是切断Si-O、Si-C等共价键的常用方法【氟离子对Si-O键和Si-C键的断裂】。另外TBAF还可以用于氟取代反应制备氟化物，用于催化Hiyama交叉偶联反应。TBAF是一种非常常见的试剂，但是其后处理非常让人头疼，很难纯化干净,反相柱层析或制备液相分离[阅读全文]
(2023-03-09 16:42:11)
pulprog:PulseProgram,suchas TDTimeDomainThisspecifiesthenumberdatapointstobetakenwiththespecifiedspectrum.AhighervalueforTDincreasesresolution,butalsoincreasesoverallacquisition time.TDvaluesaretypicallysettoapowerof2value(i.e.65536). NSNumberofscansThisissimplythenumberofscans.Increasingthenumberofscansincreasessignal‐to‐noiseratio,butalsoincreasesoverallexperimenttime. ...[阅读全文]
(2023-03-08 20:07:17)
Manystudentsaskthisquestion.Youshouldcollectenoughscansuntilthesignal-to-noiseratioisadequateforyourneeds.ForNMRmeasurements(wheresaturationisnotaproblem)thesignal-to-noiseratioincreasesasthesquarerootofthenumberofscans.Inordertodoublethesignal-to-noiseratioinaparticularspectrumonemustcollect4timesasmanyscansaswerecollectedintheoriginalspectrum.Takealookatthefigurebelowwherespectraareplottedonanab...[阅读全文]
(2023-03-08 20:04:27)
Allofyouroutinelyuseprotondecouplinginyour31PNMRspectra,manyofyouwithoutgivingitathought.Fewpeoplerealizethatitisasimplemattertodecouple31Pinyour1HNMRspectra.Thiswillallowyoutodeterminewhichprotonsarecoupledtophosphorus.Anexampleofthisisshownbelow.Thelowertraceisastandard1Hspectrumandtheuppertraceisa1Hspectrumwith31Pdecoupling.[阅读全文]
(2023-03-08 20:00:37)
Ithasalwayspuzzledmehowstudentssowillinglyacceptthefactthat13CisJcoupledtoaspinI=1nucleuslike2H(eg.themultipletsforthe13Cspectraofdeuteratedsolvents)howevertheydonotquestionthefactthat13CalmostnevershowsaJcouplingto14N(anotherspinI=1nucleus).Thereasonthat13CexhibitsJcouplingto2Histhattherelaxationamongthethreeenergylevelsof2Hisratherslowandeach13C"sees"the2HineachofitsthreeZeemanstates,s...[阅读全文]
(2023-03-08 19:51:28)
HereareyouroptionsoncollectingNMRdatawhenyouhaveonlyalimitedamountofsample.1.Useastandardsetupandgetmoresampleorcollectmorescans.Yeahyeah.....Iknow.....ifyoucoulddothisyouwouldn'thaveaproblem.
(2023-03-08 19:44:06)
ThereceivergainofanNMRspectrometerismuchlikethevolumecontrolonaradio.WhenitissettoohightherewillbedistortionintheNMRsignal.TheFIDwillbeclippednearthebeginningofthesignal.TheFouriertransformofthisdistortedsignalisadistortedNMRspectrum.Thefigurebelowshowswhatthisdistortionlookslike. Manyspectrometerswillcalculatethereceivergainautomaticallyhoweveryoushouldbeawarethatthisautomaticcalculationis...[阅读全文]
(2023-03-08 19:33:52)
ManyNMRusers(oftheorganicvariety)cometobelievethatall13Cresonancesaresingletsasthemostcommonwaytocollectthedataiswithprotondecoupling,whichindeedreducesmost13Cresonancestosinglets.Itisasurprisetosometofindmultiplicityinthe13Cresonanceswhenanucleussuchas31Por19Fispresentinthemolecule.Belowisthearomaticregionoftheprotondecoupled13CNMRspectrumofalpha,alpha,alpha-trifluoro-p-tolualdehyde(thealdehydepe...[阅读全文]
