15. Analytical Techniques:IR, NMR, Mass Spect

The reaction of (Z)-2-pentene with water and a trace of H₂SO₄ forms two products. Identify the products from their mass spectra.

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A mass spectrum shows significant peaks at m/z = 87, 115, 140, and 143. Which of the following compounds is responsible for that mass spectrum?

The mass spectrum for a compound with molecular weight of 102 is shown below. Its IR spectrum has a broad, strong absorption at 3600 cm^–1 and a medium absorption at 1360 cm^–1.

b. Show the mechanism for formation of the peak at m/z = 84.

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Propose a fragmentation to account for each numbered peak in the mass spectrum of n-butyl isopropyl ether.

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In the mass spectrum of hexan-3-ol, identify the fragments arising from two α-cleavage fragmentations and one dehydration fragmentation.

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Suggest three ways that the following tertiary amine can fragment by α-cleavage. At which m/z would you expect to see peaks corresponding to these fragments?

For each of the molecules shown, predict the structure of at least one major fragment in the mass spectrum.

(d)

For each of the molecules shown, predict the structure of at least one major fragment in the mass spectrum.

(e)

Identify the peaks in the mass spectrum of octan-4-one that correspond to (a) α-cleavage.

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For each of the molecules shown, predict the structure of at least one major fragment in the mass spectrum.

(b)

The molecular ion (M) is significant in the mass spectrum of benzyl fluoride, but it is barely present in the mass spectrum of benzyl iodide. Why might this be the case?

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The mass spectrum of tert-butylamine follows shows an intense base peak at m/z 58, and very little else. Use a diagram to show the cleavage that accounts for the base peak. Suggest why no molecular ion is visible in this spectrum.

The mass spectrum for a compound with molecular weight of 102 is shown below. Its IR spectrum has a broad, strong absorption at 3600 cm^–1 and a medium absorption at 1360 cm^–1.

a. Identify the compound.

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Using curved arrows, show the principal fragments you would expect to see in the mass spectrum of each of the following compounds:

d.

The following compounds undergo McLafferty rearrangement in the mass spectrometer. Predict the masses of the resulting charged fragments.

(b) 3-methylhexan-2-one