what is upfield & downfield in nmr spectroscopy
Answers
Answer:
NMR spectrum is a plot of the radio frequency applied against absorption.
A signal in the spectrum is referred to as a resonance.
The frequency of a signal is known as its chemical shift, d
The chemical shift in absolute terms is defined by the frequency of the resonance expressed with reference to a standard compound which is defined to be at 0 ppm. The scale is made more manageable by expressing it in parts per million (ppm) and is indepedent of the spectrometer frequency.

It is often convienient to describe the relative positions of the resonances in an NMR spectrum. For example, a peak at a chemical shift, δ, of 10 ppm is said to be downfield or deshielded with respect to a peak at 5 ppm, or if you prefer, the peak at 5 ppm is upfield or shielded with respect to the peak at 10 ppm. The terms shielded and deshielded will be explained later.
Answer:
Explanation:
NMR spectrum is a plot of the radio frequency applied against absorption.
A signal in the spectrum is referred to as a resonance.
The frequency of a signal is known as its chemical shift, d
The chemical shift in absolute terms is defined by the frequency of the resonance expressed with reference to a standard compound which is defined to be at 0 ppm. The scale is made more manageable by expressing it in parts per million (ppm) and is indepedent of the spectrometer frequency.

It is often convienient to describe the relative positions of the resonances in an NMR spectrum. For example, a peak at a chemical shift, δ, of 10 ppm is said to be downfield or deshielded with respect to a peak at 5 ppm, or if you prefer, the peak at 5 ppm is upfield or shielded with respect to the peak at 10 ppm. The terms shielded and deshielded will be explained later