Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: tripfkcdinadeucerace on July 14, 2019, 09:29:17 PM
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Hello, Im trying to determine an organic structure here is what I know:
according to solubility and other physical tests, the compound is an alcohol with 5 or fewer carbons
There are 4 distinct hydrogen environments with spin/spin splitting of triplet, triplet, singlet, singlet.
there are 3 distinct carbon environments
there is at least one primary or secondary -OH (since its an alcohol): di-ols are more likely then tri-ols which are more likely then quadr-ol, etc.
I don't have access to the actual spectra just this information so (in this case) one can assume that other functional groups are not present.
what I know:
*there can't be an ethyl-methyl tail as that would result in a triplet, quadruplet spin/spin
*OH groups produce a singlet (right? please tell me if I'm wrong but I think that all OH groups produce the same singlet due to shielding by the O atom)
* 3 carbon environments + 5 carbons or fewer means the compound has to have between 3 and 5 carbons (could be wrong... at this point, an additional carbon would be accepted if it meets the other criteria.
* boiling point of the compound is around 120 deg. C
I have been racking my brains for a few days and cannot seem to reconcile the spin/spin splitting with any of the compounds I've come up with. especially given the 5 carbons or fewer
thank you for your help,
tripfcked
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What physical tests? And what are the chemical shifts?
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idk what exact physical tests I've only been told that according to the litany of physical tests available they all came back negative for anything but an alcohol. As for chemical shifts I know that for both 13C NMR and 1H NMR they are within the limits for alkanes and (for 13 C NMR)m potentially an alkylhalide although other NMR (1H NMR) is potentially on the edge of an alkyl halide.
specifically for physical tests I also know that a simple ignition test produced blue flames with no soot or residue but a Beilstein test did not produce coloured flames so I do not believe a halide is involved.
* seems to me the blue flames are reminiscent of high concentration alcohol like setting a bottle of everclear on fire (again I could be wrong)
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IIRC compounds of the form R-OH sometimes produce a singlet in 1H NMR due to an exchange phenomenon, not a shielding phenomenon. It has been some time since I have thought about this question, so I may not be correct. What about writing down all possible isomers and then eliminating them on the basis of the NMR information that you have?
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Hello!, thank you for your helpful suggestions I think I have figured it out!!