TRAVISTRA

 IR VIBRATIONAL SPECTROSCOPY  It involves the transition between vibrational energy levels of a molecule. It arises due to the change in dipole moment with the vibration of a bond.  The vibrational spectra are given by the EM radiations in the IR region of range 500-4000cm-1  This type of spectrum is given by diatomic molecules with permanent dipole moments like HCl, H2O, and molecules with fluctuating dipole moments like CO2. These are IR-active molecules. Compounds which are IR inactive are H2 , O2, N2, Cl2  It is also called vibrational rotational spectrum since the rotational energies are smaller than vibrational energies so both vibration and rotation occur simultaneously.  It is used to establish the identity of a compound or determine the structure of a new compound. It can also predict the functional groups which absorb at definite frequencies. PRINCIPLE The movement of atoms and the chemical bonds (vibration) is like a spring and ball. The charact...

 U-V VISIBLE SPECTROSCOPY  UV-Vis spectrum results from the interaction of EM radiation in the UV-Vis region with atoms and molecules. The UV radiation region extends from 200nm to 400nm and the visible region extends from 500nm to 800nm. Organic compounds, inorganic compounds, and coordination compounds fall in the UV-Vis spectrum. THEORY The absorption of radiation in the UV-Vis region of the spectrum is dependent on the electronic structure of the absorbing species.  When a photon of a given wavelength interacts with a molecule it may cause a transition among the electronic energy levels if its energy matches with the difference in the energies of these levels. A given electronic energy level has a number of vibrational energy levels in it and each of the vibrational energy levels has a number of rotational energy levels in it. So along with the electronic transition, vibrational and rotational transitions also occur simultaneously. So electronic spectrum appears broad...

BEER LAMBERTS LAW   When a beam of monochromatic EM radiation is passed through an Absorbing solution of concentration (c), the rate of decrease in intensity(-dI) of radiation with a thickness of the solution (dx) is proportional to the intensity of the radiation (I) and concentration (c) of the solution. -dI/dx ∝ Ic  -dI/dx = kIc  -dI/I =kcdx Beer Lambert's law gives the linear relationship between the absorbance of EM radiation and the concentration of an absorber. A = εcL A is the absorbance c is the concentration L is the path length Ε is the molar extinction coefficient