Which spectroscopy, IR or NMR would you use to distinguish between (it may help
ID: 520029 • Letter: W
Question
Which spectroscopy, IR or NMR would you use to distinguish between (it may help to draw the structures of the molecules) a. 2-butanol and 2-butanal (for full credit explain what differences you expect to see in the spectroscopy of your choice.) b. Para and ethylbenzene. (for full credit explain what differences you expect to see in the spectroscopy of your choice.) Compute all the resonance structure for the para substitution of ANILINE. Show curved arrows and the positive charge at the appropriate carbon. Identify two aromatic molecules in the following list and indicate why they are aromatic and how they follow Huckel's rule.Explanation / Answer
a. The two compounds are distinguished by their IR spectrum because the spectrum for 2-butanal indicates a carbonyl stretching and the NMR indicates an aldehydic proton distinctively different from the other compound 2-butanol which hives an stretching for hydroxyl group in IR and in NMR gives an exchangeable proton and a set of methyleneoxy protons as well. Thus both the compounds are differentiated by the IR and NMR.
b. For the p-methyl toluene and ethyl benzene the NMR is an ideal tool as IR will not able to differentiate them properly. The NMR will clearly establish them. The para methyl toluene provides two peaks for the two methyl groups or a single peak in the aliphatic region and a two sets of dd signals in the aromatic region. Where as the ethyl benzene gives a totally different spectrum Ike the methyl and benzylic protons signals separately. In the aromatic region a sets of multiples for five protons is observed. Thus both the compounds are easily differentiate by the NMR spectrum.
6a. The shown arrow is bypassing the ortho position leading to a positive charge on the meta carbon. This on resonance will by pass the para carbon as well leading to the positive charge on the another meta carbon atom which completes the resonance in the ring.
6b. The cyclopentadiene cation and cyclooctatetraene are non aromatic as they do not fulfil the rule of 4n+2 rule, whereas the cycloheptatriene cation and phenantherene are aromatic as they fulfill the rule.
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