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

Step by step solution

01

Analyze the given data for compound (a)

For compound (a), we are given the molecular formula \(\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{Br}_{2}\) and NMR data with the following chemical shifts and spin types: \(2.5(\mathrm{~d}, 3 \mathrm{H})\) and \(5.9(\mathrm{q}, 1 \mathrm{H})\). We will use this information to find the structure of the compound.

02

Identify the functional groups and neighbors based on the NMR data

Based on the NMR data: - At \(\delta=2.5\), there are 3 protons with a doublet signal, which means that these protons are neighboring a single proton. - At \(\delta=5.9\), there is 1 proton with a quartet signal, which means that this proton is neighboring 3 protons.

03

Find the structure from the NMR data

Using the information from the NMR data, we can determine that there are 2 carbon atoms in the molecule, one with 3 hydrogens attached and one with 1 hydrogen attached. Since there are also 2 bromine atoms in the molecular formula, each carbon must have a bromine attached to it. The final structure for compound (a) is: CH3-CHBr2. Here are the structures for the rest of the compounds based on the same approach: - (b) : CH3-CHCl-CH2-CH2Cl - (c) : CHBr2-CH2-CHBr2 - (d) : CH3-CH2-CH2-CHO - (e) : CH3-CO-O-CH2-CH2-CH3 - (f) : CH3-CO-O-CH-CH3-CH3 - (g) : CH3-CH2-CH2-CH2-CH2-CHBr-CH3 - (h) : CH3-CH2-CH2-CO-CH2-CH3 - (i) : CH3-CH2-CH2-CH(OH)-CH2-CH=CH2 - (j) : CH3-CH2-CH-C(O)-CH(CH3)-CH2-CH3 - (k) : CH3-CH2-CH2-CH(CH3)-CHBr-CH3 - (1) : CH3-CH2-CH2-CH2-CH2-CH2-CH2Cl The step-by-step solution was demonstrated for compound (a), while the structures for all compounds were provided based on the same approach.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Understanding Organic Compound Structures

Organic chemistry is often likened to a language with molecules as words and structural formulas as their written expressions. To unlock the meaning of these 'words', we dive into the world of Nuclear Magnetic Resonance (NMR) spectroscopy, where deciphering the structure of organic compounds is akin to understanding sentences in a book.

NMR spectroscopy reveals the electronic environment of atoms within a compound by responding to the magnetic properties of atomic nuclei. When dealing with organic compounds, NMR largely focuses on the behavior of hydrogen atoms (protons), since they are abundant in organic molecules. Analyzing NMR data is a nuanced process, connecting pieces of a puzzle to reveal the full picture, much like combining individual words to form a complete sentence.

Starting with the molecular formula, one can determine the number of carbons and hydrogens, along with any other atoms present. The next step involves interpreting the NMR signals to find out how these atoms are connected. Each distinct chemical environment in the molecule results in a separate NMR signal, telling us how many carbons are adjacent to one another and what other groups or atoms are present. Taking all this information together allows us to assemble the molecular structure piece by piece.

Interpreting Chemical Shifts in NMR

The chemical shift is the bedrock of understanding an NMR spectrum. It is measured in parts per million (ppm) and indicates the environment of hydrogen atoms in the compound. Protons in different chemical environments absorb at different frequencies, and these variations are cataloged as chemical shifts. Generally, protons attached to electronegative atoms, like oxygen or nitrogen, or within aromatic structures appear downfield (higher ppm values) compared to those in aliphatic chains which appear upfield (lower ppm values).

Moreover, subtypes of signals such as singlets (s), doublets (d), triplets (t), and multiplets (m) provide clues about the number of neighboring protons. For instance, a quartet typically indicates a hydrogen atom that is adjacent to three neighboring hydrogens. By interpreting these chemical shifts and signal patterns, one can infer not only the types of atoms in the vicinity but also the probable positioning of these atoms relative to one another in the molecular framework.

Analysis of NMR Signals

Signal analysis in NMR spectroscopy is paramount in confirming the structure of organic compounds. It allows for identification of not just which atoms are neighbors but can also reveal the presence of specific functional groups. Integral to this process is understanding spin-spin coupling, which is the interaction between neighboring nuclei and gives rise to specific splitting patterns in the NMR spectrum.

For instance, in a doublet, a proton has a single neighboring proton, causing its signal to split into two peaks. A triplet indicates two adjacent protons, while a quartet is typically associated with three neighbors. Each split in the signal can further confirm the number of adjacent hydrogen atoms, assisting in building an accurate structural representation of the molecule.

In addition, the area under the NMR signal, or the integration, correlates to the number of protons contributing to that signal. These analyses, when pieced together, create a detailed picture of the entire molecule, much like a jigsaw puzzle being completed to reveal a hidden image.