Which detector is the best to use for the gas-chromatographic determination of w

Question

Which detector is the best to use for the gas-chromatographic determination of water impurities in organic solvents? Explain. b. What effect does increasing the temperature of a GC column have on the shape of the peaks (narrow them, broaden them, or have no effect)? Explain. c. Draw the proton NMR spectrum of t-butyl butyl ether. You need only to show the proper order of the signals and the correct spin-spin splitting patterns. You do not need to have the correct chemical shift values. d. Why must^13C NMR spectra be obtained using Fourier Transform techniques rather than continuous wave (as is the case with^1H NMR)? Consider the above mass spectrum. What is the formula of this compound? The exact mass is 114.1426 Da.

Explanation / Answer

a. the gas chromatographic detector to be used for the analysis of water impurities in a organic samle is mass detector also known as MS detector which meaures even the small amounts of water present in sample.

b. Increasing the temperature of the GC column would result in shorter retnetion times or faster elution of compounds. Thus the peaks would become narrow.

c. NMR for t-butyl butyl ether

Possible peaks

0.9 ppm (t, 3H) for CH3 next to CH2

1.0 ppm (sex, 2H) for CH2 between CH3 and CH2

1.2 ppm (qnt, 2H) for CH2 between CH2 and CH2

3.7 ppm (t, 2H) for CH2 next to O and CH2

1.5 ppm (s, 9H) for tert-butyl group

d. The concentration of 13C relative to 12C is very low and thus a fourier trnsform results in moderate intensity peaks over the continuous wave technique.

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