15. Analytical Techniques:IR, NMR, Mass Spect

Which of the following molecular vibrations is expected to be infrared active?

Which of the following molecular vibrations is expected to be infrared active?

Consider the IR spectrum of an unknown compound. Which absorption is most indicative of the presence of a carbonyl group ($>C=O$) in the molecule?

Which region in the IR spectrum could be used to distinguish between butanoic acid and 2-butanone?

Which of the following peaks would you expect to be labeled in the infrared (IR) spectrum of acetaminophen?

Which of the following characteristic absorption bands would you expect to observe in the IR spectrum of 2-naphthol?

Which of the following characteristic absorption bands would you expect to observe in the IR spectrum of benzyl acetate?

Which of the following characteristic absorption bands would you expect to observe in the IR spectrum of eugenol?

Which of the following characteristic absorption bands would you expect to observe in the IR spectrum of isopentyl acetate?

Would it be possible to differentiate between $C_2{H}_5\mathrm{OH}$ (ethanol) and ${\mathrm{CH}}_{3}O{\mathrm{CH}}_3$ (dimethyl ether) using infrared (IR) spectroscopy?

Which of the following correctly matches a characteristic infrared absorption peak with the corresponding functional group in aspirin?

An IR spectrum shows a strong, broad absorption around $3300-3500 \mathrm{cm}-1$ and a sharp absorption near $1700 \mathrm{cm}-1$. Which of the following molecules is most likely to produce this spectrum?

Which of the following correctly identifies the major absorption bands in the IR spectrum of triphenylmethanol?

A C-D (carbon–deuterium) bond is electronically much like a C-H bond, and it has a similar stiffness, measured by the spring constant, k. The deuterium atom has twice the mass (m) of a hydrogen atom, however.

(a) The infrared absorption frequency is approximately proportional to $\sqrt{\frac{k}{m}}$ , when one of the bonded atoms is much heavier than the other, and m is the lighter of the two atoms (H or D in this case). Use this relationship to calculate the IR absorption frequency of a typical C-D bond. Use 3000 cm^–1 as a typical C-H absorption frequency.

(b) A chemist dissolves a sample in deuterochloroform (CDCl₃) and then decides to take the IR spectrum and simply evaporates most of the CDCl₃. What functional group will appear to be present in this IR spectrum as a result of the CDCl₃ impurity?