When compound A (C5H12O) is treated with HBr, it forms compound B (C5H11Br). The 1H NMR spectrum of compound A has a 1H singlet, a 3H doublet, a 6H doublet, and two 1H multiplets. The 1H NMR spectrum of compound B has a 6H singlet, a 3H triplet, and a 2H quartet. Identify compounds A and B.

Verified step by step guidance

1. Examine the molecular formula of compound A (C5H12O) and consider possible structures, focusing on alcohols since it reacts with HBr.
2. Analyze the 1H NMR spectrum of compound A: a 1H singlet suggests an isolated proton, a 3H doublet indicates a methyl group adjacent to a CH group, a 6H doublet suggests two equivalent methyl groups adjacent to a CH group, and two 1H multiplets suggest two CH groups.
3. Consider the reaction of alcohols with HBr, which typically involves the conversion of an -OH group to a -Br group, suggesting compound B (C5H11Br) is an alkyl bromide.
4. Analyze the 1H NMR spectrum of compound B: a 6H singlet suggests two equivalent methyl groups not adjacent to any protons, a 3H triplet indicates a methyl group adjacent to a CH2 group, and a 2H quartet suggests a CH2 group adjacent to a CH3 group.
5. Propose structures for compounds A and B based on the NMR data and the reaction with HBr, ensuring the structures are consistent with the molecular formulas and NMR spectra.

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, indicated by peaks in the spectrum. The splitting patterns (singlets, doublets, triplets, etc.) reveal how many neighboring hydrogen atoms are present, which helps in deducing the connectivity of atoms in the molecule.

Substitution Reactions

Substitution reactions involve the replacement of one atom or group in a molecule with another. In this case, the treatment of compound A with HBr leads to the substitution of a hydroxyl group (-OH) with a bromine atom (-Br). Understanding the mechanism of substitution, whether it is SN1 or SN2, is crucial for predicting the structure of the resulting compound B.

Molecular Formula and Structure

The molecular formula provides essential information about the number and types of atoms in a compound. For compounds A (C5H12O) and B (C5H11Br), analyzing the molecular formula helps in deducing their structures. The presence of functional groups, such as alcohols and alkyl halides, influences the chemical behavior and spectral characteristics, which are critical for identifying the compounds.