Chemistry Notes for B.Sc. and M.Sc.

  B athochromic shift   -  It is the shift of the   absorption maxima (λ max ) of a substance   towards longer wavelengths . It is   also known as red shift .   Since, Energy (E) is inversely proportional to Wavelength. So, in Bathochromic shift----energy decreases and wavelength increases. In Bathochromic shift, energy decreases and wavelength increases. Factors causing Bathochromic shift: The bathochromic shift is caused by following: A.  Extending Conjugation i.  either by increasing double bonds ii.  or by adding electron donating groups ( like -OH, -NH 2 )   in conjugation to double bonds. B.  Solvent Effects i.  The less polar (non-polar) solvents cause bathochromic shift for n-π* transitions. ii.  The more polar (polar) solvents cause bathochromic shift for π-π* transitions. Example: Benzene shows  π-π* electronic transitions at 255 nm. Adding auxochrome NH 2   to the benzene ring makes it aniline an...