Unveiling the Secrets of Organic Molecules. The third semester MSc Organic Spectroscopy question paper aims to test the knowledge and understanding of students regarding advanced spectroscopic techniques and their applications in the structural elucidation and analysis of organic compounds.
The paper is designed to challenge students to think critically and creatively to solve problems related to spectroscopic data interpretation and analysis.
why ethylene protons are de-shielded than acetylene protons?
The protons in ethylene (C2H4) are more de-shielded than the protons in acetylene (C2H2) due to the differences in the electron density surrounding the two molecules.
In ethylene, the two carbon atoms are bonded to each other through a double bond, which consists of one sigma bond and one pi bond. The pi bond consists of two electrons that are localized in the region above and below the plane of the molecule. This electron density creates a magnetic field that opposes the external magnetic field applied during NMR spectroscopy, causing the protons in the molecule to experience a higher chemical shift and appear more de-shielded.
Unveiling the Secrets of Organic Molecules
In acetylene, the two carbon atoms are bonded to each other through a triple bond, which consists of one sigma bond and two pi bonds. The pi bonds in acetylene are more diffuse than the pi bond in ethylene, which means that the electron density is spread out over a larger region. This results in a weaker magnetic field opposing the external magnetic field, causing the protons in acetylene to experience a lower chemical shift and appear less de-shielded than the protons in ethylene.
In summary, the electron density surrounding the pi bond in ethylene is more localized and concentrated, resulting in a stronger magnetic field opposing the external magnetic field and causing the protons to appear more de-shielded in NMR spectroscopy.