Question

1. When an alcohol is diluted in a solvent that cannot form hydrogen bonds with the alcohol, which of the following changes is expected for the IR absorption signal for the O–H bond? Select all that apply. A : Cause the peak to narrow. B : Shift the peak to a higher wavenumber. C : Shift the peak to a lower wavenumber. D : Cause the peak to broaden.

2. Of the following statements regarding the base peak in a mass spectrum, which are always true. Select all that apply.

• A : The base peak is the tallest peak in the spectrum.

• B : The base peak corresponds to the peak with the smallest m/z.

• C : The base peak corresponds to the peak with the largest m/z.

• D : The base peak is furthest to the right.

• E : The base peak may not be present in spectrum.

• F : The base peak corresponds to the most abundant ion.

3. please select from the highlighted ones in (). The presence of a bromine atom in a molecule will produce a mass spectrum with an (M+2)^+• peak that is approximately (equal to or one-third or one-half)  the intensity of the molecular ion peak because the ⁷⁹Br isotope is found in (equal or greater or less) abundance compared to the ⁸¹Br isotope.

Answer 1

The following answers are based on purely fundamental and there is no reason to explain fundamentals since you are familiar with them.

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1. When an alcohol is diluted in a solvent that cannot form hydrogen bonds with the alcohol, which of the following changes is expected for the IR absorption signal for the O–H bond?

Answers to check:

A : Cause the peak to narrow

B : Shift the peak to a higher wave number

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2. Of the following statements regarding the base peak in a mass spectrum, which are always true.

Answers to check:

A : The base peak is the tallest peak in the spectrum.

F : The base peak corresponds to the most abundant ion.

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3. The presence of a bromine atom in a molecule will produce a mass spectrum with an (M+2)^+• peak that is approximately (equal to)  the intensity of the molecular ion peak because the ⁷⁹Br isotope is found in (equal) abundance compared to the ⁸¹Br isotope.

Because natural abundance of bromine is really 50% ⁷⁹Br and 50% ⁸¹Br.

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