Skip to main content

Explain the significance of magnitude of “J” constant in structure elucidations.

Q.3. (b) Explain the significance of magnitude of “J” constant in structure elucidations.
Ans.3. (b) Coupling constant: The distance between the centers of the two adjacent peaks in a multiplet is usually constant and is usually called the coupling constant. The value of the coupling constant is independent of the external field. It is measured in Hertz (Hz) or in cps (cycles per second). It is denoted by the letter J.

Illustrate the following with suitable examples

Q.3. (a) Illustrate the following with suitable examples
(i)Diamagnetic anisotropy
(ii)Correlation Spectroscopy and its significance
Ans.3. (a)
(i). Diamagnetic Anisotropy: Diamagnetic anisotropy is the shielding and deshielding depending on the orientation of the molecule with respect to the applied magnetic field.
Anisotropy is the property of a molecule in different orientations which show variations in physical properties along different axes of the molecule.

Discuss briefly the theory of ESR spectroscopy

Q.3. (a) Discuss briefly the theory of ESR spectroscopy, spin-spin splitting and its qualitative applications
Ans.3. (a) Electron Spin Resonance It is a branch of absorption spectroscopy in which radiation having frequency in the microwave region is absorbed by paramagnetic substances to induce transitions between magnetic energy levels of electrons with unpaired spins. The magnetic energy splitting is done by applying a static magnetic field.

Explain ATR phenomenon and its applications

(a) Explain ATR phenomenon and its applications
Ans.2.(a) ATRInternal reflection spectroscopy is a technique for obtaining IR spectra of samples that are difficult to deal with, such as solids of limited solubility, films, threads, pastes, adhesives, and powders. Principle when a beam of radiation passes from a denser to a less dense medium, reflection occurs. The fraction of the incident beam reflected increases as the angle of incidence becomes larger; beyond a certain critical angle, reflection is complete. It has been shown both theoretically and experimentally that during the reflection process the beam penetrate a small distance into the less dense medium before reflection occurs. 

Discuss how certain compounds produce fluorescence or phosphorescence when exposed to electromagnetic radiation. How this property is exhibited only by organic compounds with certain structural specifity?

Q.1. (c) Discuss how certain compounds produce fluorescence or phosphorescence when exposed to electromagnetic radiation. How this property is exhibited only by organic compounds with certain structural specifity? Explain
Ans.1.(c) When electromagnetic radiation passes through matter, a variety of phenomena may occur. One of them is; in some cases, the molecules after absorbing radiation become excited but they do not lose energy very quickly but with some delay. In such cases, the energy is re-emitted as radiation, usually of longer wavelength: than was originally absorbed. This phenomenon is termed as fluorescence. If in some cases, there is a detectable time delay in re-emission, the phenomenon is termed as phosphorescence.

Give principle of UV-visible spectroscopy

Q.1.(b)Give principle of UV-visible spectroscopy, Explain why cellulose is white in colour, picric acid is yellow and aromatic diazotization and coupling produces different shades.
Ans.1. (b)The wavelength range of UV radiation starts at blue end of the visible light (above 4000 A°) and ends at 2000 A°. However, the wavelength of visible radiation starts at 8000 A° and ends at 4000 A°. Spectroscopically, visible light acts in the same way as UV light.

Define fluorescence and phosphorescence

Q.1. (b) Define fluorescence and phosphorescence, Explain the effect of structural rigidity, temperature and pH on fluorescence?
Ans.1.(b) Fluorescence &Phosphorescence: Fluorescence is light energy produced by a process where high-energy radiation (such as ultraviolet or X-ray) is absorbed by electrons surrounding an atom and is re-emitted as light energy.

Explain Beer’s Law and its limitations in quantitative estimation.

Q.1. (a) Explain Beer’s Law and its limitations in quantitative estimation.
Ans.1.(a) Two separate laws governing absorption are usually known as lambert’s law and beer’s law, in the combined form they known as the beer’s-lambert law.

Define and differentiate between auxochromes and chromophores. Exemplify and explain how auxochrome shifts

Ans.1.
(a) CHROMOPHORE: The term chromophore was previously used to denote a functional group of some other structural feature of which gives a color to compound. For example- Nitro group is a chromophore because its presence in a compound gives yellow color to the compound. But these days the term chromophore is used in a much broader sense which may be defined as “any group which exhibit absorption of electromagnetic radiation in a visible or ultra-visible region “It may or may not impart any color to the compound. Some of the important chromophores are: ethylene, acetylene, carbonyls, acids, esters and nitrile groups etc.

Subscribe to Pharma Analysis