91Ó°ÊÓ

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

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.

4-Methyl-2-pentanone and 3-methylpentanal are isomers. Explain how

you could tell them apart, both by mass spectrometry and by infrared

spectroscopy.

Question: 4-Methyl-2-pentanone and 3-methylpentanal are isomers. Explain how you could tell them apart, both by mass spectrometry and by infrared spectroscopy.

Grignard reagents undergo a general and very useful reaction with

ketones. Methylmagnesium bromide, for example, reacts with cyclohexanoneto yield a product with the formula C₇H₁₄O . What is the structure of this product if it has an IR absorption at 3400 cm^-1 ?

Question: Grignard reagents undergo a general and very useful reaction with

ketones. Methylmagnesium bromide, for example, reacts with cyclohexanoneto yield a product with the formula${\mathbf{C}}_{\mathbf{7}}{\mathbf{H}}_{\mathbf{14}}\mathbf{O}$ . What is the structure of this product if it has an IR absorption at $\mathbf{3400}\mathbf{}{\mathbf{cm}}^{\mathbf{-}\mathbf{1}}$?

Ketones undergo a reduction when treated with sodium borohydride, NaBH₄

. What is the structure of the compound produced by reaction

of 2-butanone with NaBH₄ if it has an IR absorption at 3400 cm^-1 and M⁺ = 74in the mass spectrum?

Nitriles, R - C = N , undergo a hydrolysis reaction when heated with

aqueous acid. What is the structure of the compound produced by hydrolysis of propanenitrile, CH₃CH₂C=N , if it has IR absorptions from 2500-3100cm^-1 and at 1710cm^-1 , and has M⁺ = 74?

The infrared spectrum of the compound with the mass spectrum shown below lacks any significant absorption above 3000cm^-1 . There is a prominent peak near 1740cm^-1 and another strong peak near 1200cm^-1 .

Propose a structure consistent with the data.