Sketch the following spectra that would be obtained for 2-chloroethanol: b. The 1H NMR spectrum for a sample of the alcohol that contains a trace amount of acid.

Verified step by step guidance

1. Step 1: Identify the different types of protons in the molecule. 2-chloroethanol (CH3CH2OH) has three types of protons: the methyl group (CH3), the methylene group (CH2), and the hydroxyl group (OH).
2. Step 2: Determine the relative area under the curve for each type of proton. The methyl group has three protons, the methylene group has two protons, and the hydroxyl group has one proton. Therefore, the ratio of the areas under the peaks will be 3:2:1.
3. Step 3: Consider the effect of the trace amount of acid. The presence of acid can cause the OH proton to exchange rapidly with the acid protons, which can lead to a broadening or even disappearance of the OH peak.
4. Step 4: Consider the chemical shift values. The OH proton will be downfield (higher ppm) due to the electronegativity of the oxygen atom. The CH2 protons will be next, due to the electronegativity of the chlorine atom. The CH3 protons will be upfield (lower ppm).
5. Step 5: Sketch the spectrum. Draw three peaks with the appropriate relative areas and chemical shift values. Remember that the OH peak may be broad or absent due to the presence of the acid.

Key Concepts

Nuclear Magnetic Resonance (NMR) Spectroscopy

NMR spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It relies on the magnetic properties of certain nuclei, such as hydrogen-1 (1H), to provide information about the number of hydrogen atoms, their environment, and how they are connected to other atoms in the molecule. The resulting spectrum displays peaks that correspond to different hydrogen environments, allowing chemists to infer structural details.

Chemical Shifts

Chemical shifts in NMR spectroscopy refer to the variation in resonance frequency of nuclei due to their electronic environment. In 1H NMR, these shifts are measured in parts per million (ppm) and provide insight into the types of hydrogen atoms present. For example, hydrogens attached to electronegative atoms, like chlorine in 2-chloroethanol, will appear downfield (at higher ppm values) compared to those in more electron-rich environments.

Integration and Multiplicity

Integration in NMR spectroscopy quantifies the area under each peak, which correlates to the number of hydrogen atoms contributing to that signal. Multiplicity, determined by the splitting of peaks, reveals the number of neighboring hydrogen atoms (n+1 rule). In the case of 2-chloroethanol, the presence of a trace amount of acid may affect the integration and splitting patterns, providing additional information about the molecular environment and interactions.