Identify each of the following compounds from the ¹H NMR data and molecular formula:
c. C₅H₁₀O₂: a 3H triplet at 1.15 ppm
a 3H triplet at 1.25 ppm
a 2H quartet at 2.33 ppm
a 2H quartet at 4.13 ppm

Verified step by step guidance

1. Analyze the molecular formula C₅H₁₀O₂. The degree of unsaturation can be calculated using the formula: (2C + 2 - H)/2. Substituting the values, (2(5) + 2 - 10)/2 = 1. This indicates one degree of unsaturation, which could correspond to a double bond or a ring.
2. Interpret the 1H NMR data. A 3H triplet at 1.15 ppm suggests a methyl group (-CH₃) adjacent to a -CH₂- group. Similarly, a 3H triplet at 1.25 ppm also suggests another methyl group adjacent to a -CH₂- group.
3. The 2H quartet at 2.33 ppm indicates a -CH₂- group adjacent to a carbonyl group (C=O), as this chemical shift is characteristic of protons near an electron-withdrawing group like a carbonyl.
4. The 2H quartet at 4.13 ppm suggests a -CH₂- group adjacent to an electronegative atom, such as oxygen in an ester functional group (-COO-).
5. Combine the information. The molecular formula, degree of unsaturation, and NMR data suggest the compound is an ester with the structure CH₃CH₂COOCH₂CH₃. Verify this by matching the NMR data to the proposed structure.

Key Concepts

NMR Spectroscopy

Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It provides information about the number of hydrogen atoms in different environments, their connectivity, and the overall molecular structure. The chemical shifts, multiplicity, and integration of peaks in the NMR spectrum help identify functional groups and the arrangement of atoms.

Chemical Shifts

Chemical shifts in NMR spectroscopy refer to the resonance frequency of a nucleus relative to a standard in a magnetic field, measured in parts per million (ppm). Different chemical environments cause shifts in the resonance frequency, allowing chemists to infer the types of hydrogen atoms present. For example, protons attached to electronegative atoms or in different hybridization states will resonate at different ppm values.

Multiplicity and Integration

Multiplicity in NMR refers to the splitting of NMR signals due to spin-spin coupling between neighboring hydrogen atoms, which provides insight into the number of adjacent protons. Integration indicates the relative number of protons contributing to a particular signal, allowing for the determination of the ratio of different types of hydrogen in the molecule. Together, these concepts help deduce the structure of the compound based on the observed peaks.