Which parameter causes a stronger IR absorption?
Infrared absorption follows the quantum selection rule that a vibration must cause a change in molecular dipole moment to interact with oscillating infrared electric field. The absorption intensity is proportional to the square of the dipole change during motion. Highly polar bonds such as carbonyl, hydroxyl and amide groups undergo large dipole variations, yielding intense IR bands, whereas weakly polar bonds absorb poorly. Concentration influences absorbance via Beer-Lambert law, but intrinsic molecular property determining strength is dipole modulation. Thus, vibrations with substantial cha
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.