Correct option is B
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique based on re-orientation of atomic nuclei with non-zero nuclear spins in an external magnetic field. This re-orientation occurs with absorption of electromagnetic radiation in the radio frequency region from roughly 4 to 900 MHz, which depends on the isotopic nature of the nucleus and increased proportionally to the strength of the external magnetic field. Notably, the resonance frequency of each NMR-active nucleus depends on its chemical environment. As a result, NMR spectra provide information about individual functional groups present in the sample, as well as about connections between nearby nuclei in the same molecule. As the NMR spectra are unique or highly characteristic to individual compounds and functional groups, NMR spectroscopy is one of the most important methods to identify molecular structures, particularly of organic compounds.
The energy difference ΔE between nuclear spin states is proportional to the magnetic field. ΔE is also sensitive to electronic environment of the nucleus, giving rise to what is known as the chemical shift, δ.
All of the protons found in chemically identical environments within a molecule are chemically equivalent, and they often exhibit the same chemical shift. Thus, all the protons in tetramethylsilane (TMS) or all the protons in benzene, cyclopentane, or acetone—which are molecules that have protons that are equivalent by symmetry considerations—have resonance at a single value of δ (but a different value from that of each of the other molecules in the same group). Each such compound gives rise to a single absorption peak in its NMR spectrum. The protons are said to be chemically equivalent. On the other hand, a molecule that has sets of protons that are chemically distinct from one another may give rise to a different absorption peak from each set, in which case the sets of protons are chemically nonequivalent.
Nearly every nonequivalent carbon atom in an organic molecule gives rise to a peak with a different chemical shift.
To determine the number of
NMR signals, we need to analyze the unique environments of hydrogen and carbon atoms in the given bicyclic compound.
The protons experience different electronic environments due to their spatial positions and interactions with chlorine atoms. Axial and equatorial protons will exhibit different chemical shifts.
