Solution
= Solution
The products are
$$
\boxed{\mathrm B=HC{\equiv}C{-}C(CH_3)_2{-}OCH_2CH_3},
$$
$$
\boxed{\mathrm D=3{-}ClC_6H_4{-}CH_2{-}OCH_2CH_3}.
$$
B retains the terminal alkyne and replaces the tertiary propargylic chlorine with ethoxy. D replaces the benzylic chlorine while retaining the aromatic chlorine; its meta arrangement follows from the drawn starting material, rather than from four aromatic protons alone.
|| Product
|| Proton shift / ppm
|| Assignment
| B
| 1.21, 3H triplet
| Ethoxy terminal methyl, coupled to the adjacent two protons.
| B
| 1.46, 6H singlet
| Two equivalent methyl groups on the substituted carbon, with no neighboring proton to split them.
| B
| 2.66, 1H singlet
| Terminal alkyne proton.
| B
| 3.59, 2H quartet
| Ethoxy methylene next to oxygen, coupled to its methyl group.
| D
| 1.18, 3H triplet; 3.58, 2H quartet
| The ethoxy group, with a common approximately 7 Hz coupling.
| D
| 4.80, 2H singlet
| Benzylic methylene attached to oxygen, with no vicinal aliphatic proton.
| D
| Two aromatic multiplet regions, 4H total
| The four remaining ring protons of the disubstituted aromatic ring.
For B, the strong $3300\,\mathrm{cm^{-1}}$ band is the terminal sp C–H stretch, the $2950\,\mathrm{cm^{-1}}$ band is aliphatic C–H stretching, and the weak $2100\,\mathrm{cm^{-1}}$ band is the alkyne stretch. The terminal proton and alkyne band together distinguish this from an alcohol interpretation of the high-frequency absorption.
For D, $3050\,\mathrm{cm^{-1}}$ is aromatic C–H stretching, $2950\,\mathrm{cm^{-1}}$ is aliphatic C–H stretching, and the $1600$ and $1580\,\mathrm{cm^{-1}}$ bands are aromatic skeletal stretches. The listed spectrum is a selected peak list, so omission of a C–O band is not evidence that the ether bond is absent.
\Image[/past-exam-of-the-mphil-in-micro-and-nanotechnology-enterprise-course-of-the-university-of-cambridge/2023/paper-1-additional-organic-products.png]
{title=Derived ether products and the competing elimination product}
{description=Original skeletal drawings of B, D and F. B and D retain the unsaturation indicated by the spectral data; F is the conjugated enyne formed by loss of hydrogen chloride from the tertiary propargylic substrate.}