Given the ¹H NMR spectrum and the molecular formula, suggest a structure for each molecule. [The IR spectrum suggests the presence of two C=O bonds.]
(a) Important IR bands (cm ⁻ ¹) : 1728, 1708 [Note: The pKₐ of this molecule is around 10.]
<IMAGE>

Verified step by step guidance

1. Examine the IR spectrum data: The presence of two C=O bonds is indicated by the IR bands at 1728 cm⁻¹ and 1708 cm⁻¹. These are characteristic of carbonyl groups, such as ketones or aldehydes.
2. Consider the molecular formula and the pKₐ value: A pKₐ around 10 suggests the presence of an acidic hydrogen, possibly indicating a carboxylic acid or a similar functional group.
3. Analyze the ¹H NMR spectrum: Look for signals that correspond to protons near the carbonyl groups. This can help identify the specific environment of the protons and provide clues about the structure.
4. Combine the IR and NMR data: Use the information from both spectra to hypothesize possible structures. The presence of two carbonyl groups and an acidic hydrogen suggests a dicarboxylic acid or a similar compound.
5. Propose a structure: Based on the spectral data and the molecular formula, suggest a structure that fits all the given information, ensuring that it accounts for the two C=O bonds and the acidic hydrogen.

Key Concepts

¹H NMR Spectroscopy

¹H NMR (Proton Nuclear Magnetic Resonance) spectroscopy is a technique used to determine the structure of organic compounds by analyzing the magnetic environment of hydrogen atoms. It provides information about the number of hydrogen atoms, their chemical environment, and how they are connected within a molecule. Peaks in the spectrum correspond to different hydrogen environments, and their splitting patterns can indicate neighboring hydrogen atoms.

IR Spectroscopy and Functional Groups

Infrared (IR) spectroscopy is used to identify functional groups in a molecule by measuring the absorption of infrared light, which causes molecular vibrations. Specific absorption bands correspond to different functional groups. In this question, the presence of two C=O bonds is indicated by IR bands at 1728 and 1708 cm⁻¹, suggesting the presence of carbonyl groups, such as ketones or aldehydes, which are crucial for determining the molecular structure.

pKₐ and Acid-Base Properties

The pKₐ value of a molecule indicates the acidity of a hydrogen atom within the molecule, reflecting how easily it can donate a proton. A pKₐ around 10 suggests the presence of a moderately acidic hydrogen, often associated with functional groups like carboxylic acids or phenols. Understanding the pKₐ helps in identifying possible acidic sites in the molecule, which is essential for proposing a plausible structure.