% Transmittance 4000 8 3800 3600 3400 3200 3000 2800 2600 2400 2200 7 16 4.6 J 4.5 4.4 5 nww Mumm 2000 4.3 PPM 1800 1 1600 Wavenumber (cm¹) 4 8 (ppm) 1400 3 I I I 1200 II 1000 2 1 I 800 0 600

Shown are the H NMR spectra for 2 isomeric compounds three and four of the formula C5H10O. The IR spectrum of both have an absorption in the region of 1700 to 1730 cm-1. Provide the structure for each compound, and which hydrogen atoms give rise to the peaks in each spectrum. The peak at 7.27 ppm can be ignored, and the red numbers are integration values.

Chapter 18 Worksheet 18-1 Properties of Light 1. The stretching frequency of a carbonyl (C=0) bond in a typical ketone is 5.15 x 1013 Hz. The vibrational energy of the molecule increases when light of this frequency is absorbed.   a) What is the wavelength of this light in nanometers? b) What is the wavelength of this light in micrometers? c) Express the frequency of this light in wavenumbers. d) What is the energy (in joules) of a single photon of light at this frequency? e) What is the energy (in kilojoules) of one mole of photons at this frequency? f) Into what region of the electromagnetic spectrum does this radiation fall?

Suggest structures given the 1H NMR spectra and formulas for each of the compounds below. C4H10O

The IR spectrum, 1H NMR spectrum, and 13C NMR spectrum for the unknown compound with the formula C5H12O are given below. Make a structure for the unknown and assign the peaks in the spectra by the provided tables.

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Identify the structure of the compound a having the following IR, 1H NMR spectra (integrals shown in the boxes). Label the spectra with the information (functional groups, number of protons, formula, etc.) you obtain Compound a.  Formula: C7H14O Questions that may help you to decide: What is the element of unsaturation of the molecular formula? Show the math you use: What are the functional groups present in this molecule? Show all of them below. Draw at least two possible structures that have the required element of unsaturation as well as the observed functional groups. Based on the 1H NMR of compound a above, what molecular fragmentations do you see: Draw your final decision of the structure of compound a below:

By examining the carbon NMR spectra of 1,1-dichlorocyclohexane and cis-1,2- dichlorocyclohexane, what TWO things would you look for to distinguish between the spectra. Use structures to explain your answer.

Keeping with the theme of autumn, one of Dr. Danahy’s favorite molecules is caffeic acid due to its presence in pumpkins. This structure serves as an antioxidant and is one of many found within pumpkins. Despite its name, it bears no resemblance to caffeine. Answer the following questions about caffeic acid. The carbonyl stretch for caffeic acid is unusually low for a carboxylic acid at 1646 cm-1. For reference, the carbonyl stretch for propanoic acid is 1716 cm-1. Explain why the carbonyl stretch occurs at a lower wavenumber for caffeic acid.