Question

The red fox (Vulpes vulpes) uses a chemical communication system based on scent marks in urine. One component of fox urine is a sulfide whose mass spectrum has \(\mathrm{M}^{+}=116 .\) IR spectroscopy shows an intense band at \(890 \mathrm{~cm}^{-1}\), and \({ }^{1} \mathrm{H}\) NMR spectroscopy reveals the following peaks:\(1.74 \delta(3 \mathrm{H},\) singlet \() ; 2.11 \delta(3 \mathrm{H},\) singlet \() ; 2.27 \delta(2 \mathrm{H},\) triplet \(, J=4.2 \mathrm{~Hz})$$2.57 \delta(2 \mathrm{H},\) triplet, \(J=4.2 \mathrm{~Hz}) ; 4.73 \delta(2 \mathrm{H},\) broad \()\)Propose a structure consistent with these data. [Note: \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{~S}\) absorbs at \(2.1 \delta .]\)

Short answer

The compound is likely \(\mathrm{CH}_3\mathrm{SCH}_2\mathrm{CH}_2\mathrm{OH}\).

Step-by-step solution

Analyze Mass Spectrum

The molecular ion peak (\(\mathrm{M}^+\)) at 116 suggests the molecule has a molecular weight of 116. Considering common elements (C, H, S, O) that might make up the molecule, a likely formula could be \(\mathrm{C}_4\mathrm{H}_{10}\mathrm{S}\).

Interpret IR Spectroscopy

The intense band at \(890\ \mathrm{cm}^{-1}\) is characteristic of C-S stretching vibrations. This indicates the presence of a sulfide sulfur atom in the structure.

Analyze \(^1\mathrm{H}\) NMR Spectroscopy

1. **1.74 \(\delta\)**: Singlet for 3H, could be a \(\mathrm{-CH}_3\) group.2. **2.11 \(\delta\)**: Singlet for 3H, similar chemical shift to \(\mathrm{(CH}_3)_2\mathrm{S}\), suggesting a methyl group next to sulfur.3. **2.27 \(\delta\)**: Triplet for 2H, \(J=4.2\ \mathrm{Hz}\), likely part of \(\mathrm{-CH}_2\mathrm{-CH}_2\).4. **2.57 \(\delta\)**: Triplet for 2H, \(J=4.2\ \mathrm{Hz}\), another \(\mathrm{-CH}_2-\) group probably adjacent to sulfur.5. **4.73 \(\delta\)**: Broad for 2H, possibly indicating exchangeable protons such as from an alcohol group or thiol.

Propose a Molecular Structure

Combining all the information, a structure is proposed: \(\mathrm{CH}_3\mathrm{SCH}_2\mathrm{CH}_2\mathrm{OH}\). This structure has two methyl groups (one bonded to sulfur), a thiol linkage, an ethyl segment, and a hydroxyl group, aligning with the mass and spectroscopy data.

Key concepts

Molecular Ion Peak

In mass spectrometry, the molecular ion peak is crucial as it provides the molecular weight of the compound being analyzed. This peak is represented as \(\mathrm{M}^{+}\). In our example, the molecular ion peak at 116 indicates that the total molecular weight of the compound is 116 amu (atomic mass units). This information helps us to narrow down the possible molecular formulas for the compound.

For instance, knowing the likely elements involved (such as carbon \(\mathrm{C}\), hydrogen \(\mathrm{H}\), and sulfur \(\mathrm{S}\)), we can propose possible formulas like \(\mathrm{C}_4\mathrm{H}_{10}\mathrm{S}\). The molecular ion peak is often the starting point for chemical structure analysis, as it sets the stage for combining data from other spectrometric techniques to reveal the molecule's identity.

IR Spectroscopy

Infrared (IR) spectroscopy is a powerful tool that aids in identifying functional groups within a molecule by measuring vibrational transitions. In this context, the presence of an intense band at \(890\ \mathrm{cm}^{-1}\) gives us critical clues.

This specific band is indicative of C-S stretching vibrations, which strongly suggests the presence of a sulfide group in the molecule. Functionalgroup identification is a key step in assembling the puzzle of the molecule's structure, and IR spectroscopy provides specific, often characteristic peaks that serve as fingerprints for common functional parts of a compound.

By linking observed bands with known frequencies, chemists can deduce whether features like sulfides, hydroxyl groups, or aromatic rings are present in the sample.

NMR Spectroscopy

Nuclear Magnetic Resonance (NMR) spectroscopy offers insights into the environment of hydrogen atoms within a molecule. In this analysis, \(^1\mathrm{H}\) NMR data is quite revealing, showing multiple peaks that enable us to deduce specific structural features of the compound.

- **1.74 \(\delta\)** singlet indicates a \(\mathrm{-CH}_3\) group due to the single sharp peak.- **2.11 \(\delta\)** singlet matches a methyl group situated near sulfur, aligning with known chemical shifts.- **2.27 \(\delta\)** and **2.57 \(\delta\)** triplets are representative of \(\mathrm{-CH}_2-\) groups. Their similar coupling constant of \(J=4.2\ \mathrm{Hz}\) suggests they form part of the same ethyl chain or environment.- **4.73 \(\delta\)** broad peak possibly indicates exchangeable protons, suggesting the presence of an -OH (hydroxyl) group.

Each peak provides a piece of the structural puzzle by revealing how neighboring atoms affect the electronic environment and, consequently, the chemical shift of hydrogen atoms. This data is crucial for assembling the spatial layout of the compound.

Chemical Structure Analysis

Chemical Structure Analysis is essentially the process of piecing together all the data from various spectroscopic techniques to construct a plausible molecular structure. By combining the mass spectrometry, IR spectroscopy, and NMR spectroscopy insights, chemists can propose a coherent molecular model.

Given the data for the initial problem: a molecular ion peak at 116, alongside IR indication of sulfur, and NMR peaks relating to methyl, ethyl, and an OH group, a plausible structure is \(\mathrm{CH}_3\mathrm{SCH}_2\mathrm{CH}_2\mathrm{OH}\).

- This structure aligns with a molecular weight of 116.- It contains a C-S bond confirmed by IR.- Matches the NMR details: methyl groups near sulfur, two \(\mathrm{CH}_2\) segments, and a hydroxyl group.

Chemical structure analysis not only confirms the identity of a compound but also helps in understanding its reactivity and properties, which are important for applications in areas such as pharmaceuticals, environmental science, and materials chemistry.