Chapter 12: Structure Determination: Mass Spectroscopy and Infrared Spectroscopy

Show how you might use a Wittig reaction to prepare the following alkenes. Identify the alkyl halide and the carbonyl components.

a.

b.

Phenol,${\mathbf{C}}_{\mathbf{6}}{\mathbf{H}}_{\mathbf{5}}\mathbf{OH}$, is a stronger acid than methanol, ${\mathbf{CH}}_3\mathbf{OH}$, even though both contain an OH bond. Draw the structures of the anions resulting from loss of ${\mathbf{H}}^{\mathbf{+}}$from phenol and methanol, and use resonance structures to explain the difference in acidity.

How would you prepare the following substances from 2-cyclohexenone? More than one step may be needed.

a.

b.

c.

d.

Question: 21-62 What is the structure of the polymer produced by treatment of $\mathbf{\beta }\mathbf{-}\mathbf{propiolactone}$with a small amount of hydroxide ion?

How would you synthesize the following substances from benzaldehyde and any other reagents needed?

a.

b.

c.

Question:21-64How would you distinguish spectroscopically between the followingisomer pairs? Tell what differences you would expect to see.
(a) N-Methylpropanamide and N,N-dimethylacetamide
(b) 5-Hydroxypentanenitrile and cyclobutanecarboxamide
(c) 4-Chlorobutanoic acid and 3-methoxypropanoyl chloride
(d) Ethyl propanoate and propyl acetate

Question: 21-65 Propose a structure for a compound, ${\mathbf{C}}_{\mathbf{4}\mathbf{}}{\mathbf{H}}_{\mathbf{7}\mathbf{}}{\mathbf{ClO}}_{\mathbf{2}}$, that has the following

IR and¹H NMR spectra:

Question: 21-66 Assign structures to compounds with the following ¹H N MR spectra:

$$\begin{gathered} \left(a\right){\mathbf{C}}_{\mathbf{4}}\mathbf{}{\mathbf{H}}_{\mathbf{7}}\mathbf{}\mathbf{ClO} \\ \mathbf{IR}\mathbf{}\mathbf{:}\mathbf{1810}\mathbf{}{\mathbf{cm}}^{\mathbf{-}\mathbf{1}} \end{gathered}$$

$$\begin{gathered} \left(b\right){\mathbf{C}}_{\mathbf{6}\mathbf{}}{\mathbf{H}}_{\mathbf{7}}\mathbf{}{\mathbf{NO}}_{\mathbf{2}} \\ \mathbf{IR}\mathbf{:}\mathbf{2250}\mathbf{,}\mathbf{1735}\mathbf{}{\mathbf{cm}}^{\mathbf{-}\mathbf{1}} \end{gathered}$$

1. Question:21-67 The following reactivity order has been found for the basic hydrolysis of p-substituted methyl benzoates:$\mathit{Y}\mathbf{=}\mathit{N}{\mathit{O}}_{\mathbf{2}}\mathbf{>}\mathit{B}\mathit{r}\mathbf{>}\mathit{H}\mathbf{>}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{>}\mathit{O}\mathit{C}{\mathit{H}}_{\mathbf{3}}$
2. How can you explain this reactivity order? Where would you expect $\mathit{Y}\mathbf{=}\mathit{C}\mathbf{=}\mathit{N}\mathbf{,}\mathbf{}\mathit{Y}\mathbf{=}\mathit{C}\mathit{H}\mathit{O}\mathbf{,}\mathbf{}\mathit{a}\mathit{n}\mathit{d}\mathit{Y}\mathbf{=}\mathit{N}{\mathit{H}}_{\mathbf{2}}$to be in the reactivity list?

The heat of hydrogenation for allene (Problem 7-61) to yield propane is -295 kJ/mol, and the heat of hydrogenation for a typical monosubstituted alkene, such as propene, is -125 kJ/mol. Is allene more stable or less stable than you might expect for a diene? Explain.