Dear All,
tilt in HMBC correlations:
Someone asked recently about the tilt of the correlations in HMBC spectra, don't know if they were talking about the passive or active couplings but in any case the tilt (which is what the guy was describing as best I could tell) is determined by the sign of the proton-carbon (or whatever nucleus) couplings. This can provide useful structural information in particular cases - distinction between 2 and 3 bond couplings when the coupling is large, see for example: ''Identification of the Major Tautomer for an Etheno Adduct of 2,6-Diaminopurine by Determination of the Sign of nJH,C'', Mattias U. Roslund, Piritta Virta, and Karel D. Klika, Organic Letters, 2004, 6, 2673.
autotune comment:
And since I am writing. although a firm believer in all things automated etc etc (as long as they work, do a better job, improve efficiency and all the rest of the obvious), I have noticed to my chagrin a limitation for autotuning that was unexpected (but since I have been quite dissatisfied with our autotuning system, my reaction has been indifferent): a large change in the tuning due to a liquids sample of high ionic strength always alerted me to the fact that it might be worth checking the pulse widths before embarking on multipulse exps etc. On our system at least it, is not so easy to follow/determine that a large change in the tune has been effected for our autotune probes and I am left oblivious and seem unable to ascertain such even if actively following the progress of the tune. (We have Bruker Avance if anyone feels compelled to comment.)
solids Q:
Related to the above, is the same phenomenon seen for solid samples as for liquids of high ionic strength ? Comments or directives please.
KDK
Received on Mon Jul 24 2006 - 12:04:06 MST