tag:blogger.com,1999:blog-3300702123878659843.post239341034782791884..comments2024-03-26T05:25:50.831-04:00Comments on University of Ottawa NMR Facility Blog: Why Does My Quaternary Alkyne Carbon Show Up in My 13C DEPT Spectrum?Glenn Faceyhttp://www.blogger.com/profile/05146575170575279335noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-3300702123878659843.post-68531422195361437242020-04-07T09:52:48.439-04:002020-04-07T09:52:48.439-04:00Karl,
Thank you for your email. Yes, I suspect th...Karl,<br />Thank you for your email. Yes, I suspect that the C-H carbon of your alkyne is of the wrong phase because of the unusually large C-H coupling constant. You could confirm this by rerunning the experiment with a delay optimized for ~ 250 Hz coupling rather than 145 Hz.<br />GlennGlenn Faceyhttps://www.blogger.com/profile/05146575170575279335noreply@blogger.comtag:blogger.com,1999:blog-3300702123878659843.post-88252366853849305172020-04-07T02:09:47.940-04:002020-04-07T02:09:47.940-04:00Hi,
thank you for your interesting and informativ...Hi,<br /><br />thank you for your interesting and informative blog!<br /><br />I also made an interesting observation with alkynes. In the 13C APT spectrum the CH Signal of the alkynes is positive and not negative as expected. I guess this is also due to unusual coupling contants.<br /><br />KarlKarlnoreply@blogger.comtag:blogger.com,1999:blog-3300702123878659843.post-34627456501915925782019-05-23T15:01:11.123-04:002019-05-23T15:01:11.123-04:00Thanks a lot for your answer. I will check the pul...Thanks a lot for your answer. I will check the pulse but I don’t think so .. maybe your second idea! <br />AL Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3300702123878659843.post-89951252604013074632019-05-22T15:15:06.144-04:002019-05-22T15:15:06.144-04:00Anonymous,
Could it be that the proton channel of ...Anonymous,<br />Could it be that the proton channel of your probe is poorly tuned? or the 1H pulses poorly calibrated?<br /><br />https://u-of-o-nmr-facility.blogspot.com/2007/10/proton-probe-tuning-for-13c-detected.html<br /><br />Otherwise it may have something to do with unusually large two-bond 1H-13C coupling constants.<br /><br />Glenn Glenn Faceyhttps://www.blogger.com/profile/05146575170575279335noreply@blogger.comtag:blogger.com,1999:blog-3300702123878659843.post-28582722752120370462019-05-22T14:56:32.081-04:002019-05-22T14:56:32.081-04:00Thanks a lot !
Do you know why CH2 of epoxide app...Thanks a lot ! <br />Do you know why CH2 of epoxide appear like CH in DEPT135? <br />Thanks Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3300702123878659843.post-90933324586112651262019-03-08T12:45:04.864-05:002019-03-08T12:45:04.864-05:00I have isolated a molecule from plant source where...I have isolated a molecule from plant source where the quarternary carbons bearing OH groups on the adjacent atoms at ring junction of two fused rings do not disappear in DEPT.Anonymoushttps://www.blogger.com/profile/05898030318820684861noreply@blogger.comtag:blogger.com,1999:blog-3300702123878659843.post-56075471876770366162017-03-06T10:21:33.190-05:002017-03-06T10:21:33.190-05:00Anonymous,
I don't know of any off-hand. You ...Anonymous,<br />I don't know of any off-hand. You should consult tables of 2JCH coupling constants.<br />GlennGlenn Faceyhttps://www.blogger.com/profile/05146575170575279335noreply@blogger.comtag:blogger.com,1999:blog-3300702123878659843.post-66727184625157045952017-03-06T04:43:14.376-05:002017-03-06T04:43:14.376-05:00Hi, are there other examples for substructures wit...Hi, are there other examples for substructures with large 2-bond carbon/proton coupling constant in addition to the alkynes?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3300702123878659843.post-91659658063822164542014-07-07T13:36:51.229-04:002014-07-07T13:36:51.229-04:00Thanks Glenn - this was very helpful. My group is...Thanks Glenn - this was very helpful. My group is making compounds derived from 4-pentyn-1-ol and we also see the quaternary carbon show up in our DEPT135 spectra. This clears up a lot of confusion for us.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3300702123878659843.post-4974931226870174222012-06-04T10:15:49.550-04:002012-06-04T10:15:49.550-04:00Dear crash012,
DEPT experiments include a delay r...Dear crash012,<br /><br />DEPT experiments include a delay related to the reciprocal of the 1-bond carbon/proton coupling constant. When a quaternary carbon exhibits a large 2-bond carbon/proton coupling constant, it will appear in a DEPT spectrum. The alkynes have large 2-bond carbon/proton couplings.<br /><br />GlennGlenn Faceyhttps://www.blogger.com/profile/05146575170575279335noreply@blogger.comtag:blogger.com,1999:blog-3300702123878659843.post-28879986691701241172012-05-30T21:01:09.665-04:002012-05-30T21:01:09.665-04:00can you please provide us with other examples in w...can you please provide us with other examples in which a Quaternary carbon apperas on the DEPT135 spectra on the positive phase and if it possible a more detailed explanation on the reason behind it.crash012https://www.blogger.com/profile/07734834049854728992noreply@blogger.com