Question

Write structural formulas for the following compounds. \(\delta 2.5(\mathrm{~d}, 3 \mathrm{H})\) and \(5.9(q, 1 \mathrm{H})\) \(\delta 1.60(\mathrm{~d}, 3 \mathrm{H}), 2.15(\mathrm{~m}, 2 \mathrm{H}), 3.72(\mathrm{t}, 2 \mathrm{H})\), and \(4.27(\mathrm{~m}, 1 \mathrm{H})\) \(83.6(\mathrm{~s}, 8 \mathrm{H})\) \(\delta 1.0(\mathrm{t}, 3 \mathrm{H}), 2.1(\mathrm{~s}, 3 \mathrm{H})\), and \(2.4\) (quartet, 2H) \(\delta 1.2(\mathrm{t}, 3 \mathrm{H}), 2.1(\mathrm{~s}, 3 \mathrm{H})\), and \(4.1\) (quartet, \(2 \mathrm{H})\); contains an ester \(\delta 1.2(\mathrm{t}, 3 \mathrm{H}), 2.3\) (quartet, \(2 \mathrm{H})\), and \(3.6(\mathrm{~s}, 3 \mathrm{H})\); contains an ester \(\delta 1.1(\mathrm{~d}, 6 \mathrm{H}), 1.9(\mathrm{~m}, 1 \mathrm{H})\), and \(3.4(\mathrm{~d}, 2 \mathrm{H})\) \(\delta 1.5(\mathrm{~s}, 9 \mathrm{H})\) and \(2.0(\mathrm{~s}, 3 \mathrm{H})\) \(\delta 0.9(\mathrm{t}, 6 \mathrm{H}), 1.6(\) sextet, \(4 \mathrm{H})\), and \(2.4(\mathrm{t}, 4 \mathrm{H})\) \(\delta 1.2(\mathrm{~d}, 6 \mathrm{H}), 2.0(\mathrm{~s}, 3 \mathrm{H})\), and \(5.0\) (septet, 1H) \(\delta 1.1(\mathrm{~s}, 9 \mathrm{H})\) and \(3.2(\mathrm{~s}, 2 \mathrm{H})\) \(\delta 1.1(\mathrm{~s}, 9 \mathrm{H})\) and \(1.6(\mathrm{~s}, 6 \mathrm{H})\) (a) \(\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{Br}_{2}\) : (b) \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{Cl}_{2}\) : (c) \(\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{Br}_{4}\) : (d) \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}\) : (e) \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2}\) : (f) \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2}\) = (g) \(\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{Br}\) : (h) \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2}\) = (i) \(\mathrm{C}_{7} \mathrm{H}_{14} \mathrm{O}\) : (j) \(\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}=\) (k) \(\mathrm{C}_{s} \mathrm{H}_{11} \mathrm{Br}\) : (l) \(\mathrm{C}_{7} \mathrm{H}_{15} \mathrm{Cl}\)

Short answer

Question: Write the structural formulas for compounds a and b by analyzing the given NMR data and molecular formulas. Compound a: \(\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{Br}_{2}\), NMR data: \(\delta 2.5 (d, 3H), 5.9 (q, 1H)\) Compound b: \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{Cl}_{2}\), NMR data: \(\delta 1.60 (d, 3 H), 2.15 (m, 2 H), 3.72 (t, 2 H), 4.27 (m, 1 H)\) Answer: Compound a: \(\ce{CH2Br-CHBr2}\) Compound b: \(\ce{CH2Cl-CH2-CHCl-CH3}\)

Step-by-step solution

Analyze the NMR data

We are given the following NMR data: \(\delta 2.5(\mathrm{~d}, 3 \mathrm{H})\) and \(5.9(q, 1 \mathrm{H})\).

Construct the structure from the given molecular formula

There are two carbon atoms, four hydrogen atoms, and two bromine atoms in the compound. One possibility is to have a dibromoethane structure.

Match the NMR data to the constructed structure

The chemical shift at \(\delta 2.5\) corresponds to a doublet with 3 protons, which could possibly be the 3 equivalent H atoms connected to a carbon that is bonded to a bromine atom. Meanwhile, the chemical shift at \(\delta 5.9\) corresponds to a quartet with 1 proton, which could possibly be the single H atom connected to a carbon that is bonded to the second bromine atom.

Write the structural formula

Considering the given molecular formula and the respective NMR data, the structural formula for compound a is: \(\ce{CH2Br-CHBr2}\). Compound b: \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{Cl}_{2}\):

Analyze the NMR data

We are given the following NMR data: \(\delta 1.60(\mathrm{~d}, 3 \mathrm{H}), 2.15(\mathrm{~m}, 2 \mathrm{H}), 3.72(\mathrm{t}, 2 \mathrm{H})\), and \(4.27(\mathrm{~m}, 1 \mathrm{H})\).

Construct the structure from the given molecular formula

There are four carbon atoms, eight hydrogen atoms, and two chlorine atoms in the compound. One possibility is to have a dichlorobutane structure with chlorine atoms at different positions.

Match the NMR data to the constructed structure

The chemical shifts correspond to different hydrogen atom environments in the molecule. The \(\delta 1.60\) could be the H atoms connected to a carbon bonded to a chlorine atom. The other chemical shifts at \(\delta 2.15\), \(\delta 3.72\), and \(\delta 4.27\) correspond to H atoms within different magnetic environments due to the positions of the chlorine atoms.

Write the structural formula

Considering the given molecular formula and the respective NMR data, the structural formula for compound b is: \(\ce{CH2Cl-CH2-CHCl-CH3}\). For the rest of the compounds, follow the same approach by first analyzing the NMR data, constructing a possible structure based on the given molecular formula, matching the NMR data to the possible structure, and finally writing the structural formula.