91Ó°ÊÓ

Question: At what approximate positions might the following compounds showIR absorptions?

(f)

Identify all the acidic hydrogens ($\mathit{p}{\mathit{K}}_{\mathbf{a}}\mathbf{<}\mathbf{25}$) in the following molecules:

Base treatment of the following α,β-unsaturated carbonyl compound yields an anion by removal of H⁺ from the$\mathit{γ}$carbon. Why are hydrogens on the$\mathit{γ}$carbon atom acidic?

Although the Diels–Alder reaction generally occurs between an electron rich diene and an electron-deficient dienophile, it is also possible to

have inverse-demand Diels–Alder reactions between suitable electrondeficient

conjugated double bonds and electron-rich alkenes. These reactions are particularly useful because they allow for the incorporation of heteroatoms into the new six-membered ring. Predict the products of each inverse-demand Diels–Alder reaction below. Be sure your products reflect the correct stereochemistry. If more than one region isomer is possible, draw both.

(a)

(b)

(c)

Treatment of 1-phenyl-2-propenone with a strong base such as LDA does not yield an anion, even though it contains a hydrogen on the carbon atom next to the carbonyl group. Explain.

Question:The mass spectrum (a) and the infrared spectrum (b) of an unknown hydrocarbon are shown. Propose as many structures as you can.

Question: The mass spectrum (a) and the infrared spectrum (b) of another unknown hydrocarbon are shown. Propose as many structures as you can.

Assign Cahn–Ingold–Prelog rankings to the following sets of substituents

a.$\mathbf{−}\mathit{C}\mathit{H}\mathbf{=}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathbf{,}\mathbf{−}\mathit{C}\mathit{H}{\mathbf{\left(}\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{\right)}}_{\mathbf{2}}\mathbf{,}\mathbf{−}\mathit{C}{\mathbf{\left(}\mathbf{C}{\mathbf{H}}_{\mathbf{3}}\mathbf{\right)}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{C}{\mathit{H}}_{\mathbf{3}}$

b.$\mathbf{−}\mathit{C}{\mathit{O}}_{\mathbf{2}}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}\mathit{O}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{O}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{C}{\mathit{H}}_{\mathbf{3}}$

c.$\mathbf{−}\mathit{C}{\mathit{O}}_{\mathbf{2}}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}\mathit{O}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{O}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{C}{\mathit{H}}_{\mathbf{3}}$

d.$\mathbf{−}\mathit{C}{\mathit{O}}_{\mathbf{2}}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}\mathit{O}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{O}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{C}{\mathit{H}}_{\mathbf{3}}$,$\mathbf{−}\mathit{C}{\mathit{O}}_{\mathbf{2}}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}\mathit{O}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{O}\mathit{C}{\mathit{H}}_{\mathbf{3}}\mathbf{,}\mathbf{−}\mathit{C}{\mathit{H}}_{\mathbf{2}}\mathit{C}{\mathit{H}}_{\mathbf{3}}$

Identify each pair of relationships among the groups in glucose (pink–blue, pink–dark blue, pink–black, blue–dark blue, blue-black, dark blue-black) as cis or trans.

Propose structures for compounds that meet the following descriptions:

1. An optically active compound C₅H₁₀Owith an IR absorption at 1730 cm^-1.
2. A non-optically active compound C₅H₉N with an IR absorption at 2215cm^-1.