Discuss the type of electronic transition involved in FTIR absorption and RAMAN

Question

Discuss the type of electronic transition involved in FTIR absorption and RAMAN scattering of molecules. Describe the basic fundamental theory behind the Surface Enhanced RAMAN Spectroscopy (SERS). Identify Raman active and IR active vibrational modes in chloroacetonitrile (CICH_2CN) Discus the basics and the instrumentation involved in A) Quadrupole mass analyzer. B) Time of Flight Mass Analyzer a. Describe the mechanisms involved in separation of a multi-component mixture into its components by a) Gas Chromatography b) Reverse Phase-HPLC (RP-HPLC) and c) Size Exclusion Chromatography. A GC instrument is equipped with an open tubular column coated with a polar liquid. Following mixtures containing listed below are separated using this GC. List the elution order of these compounds starting with shorter elution lime and justify your answer. CH3CH2CHO, CH3CH2COCH3. CH3CH2CH2COOCH3 CH3CH2CH20H, CH3CH2CH2CH20H, CH3CH2CH2CH2COOH What is the order in which the following compounds would be eluted using RP- HPLC? Benzene, diethyl ether, n-hexane Acetone, dichloromethane, acetamide Isopropanol, acetic acid, catechin

Explanation / Answer

4. a) If the column is coated with a polar liquid, then it will retain the polar molecules and it will elute the apolar ones. We must recall that some organic molecules might be polar if they have 1 oxygen per 4 carbons, this last is the criteria we are going to use.

the elution order will be

i) CH3CH2CH2COOCH3, CH3CH2CHO, CH3CH2COCH3

ii) CH3CH2CH2CH2COOH, CH3CH2CH2OH, CH3CH2CH2CH2OH

b) the RP-HPLC is a method where we use an apolar solution as stationary phase, then all polar molecules will elute faster than the apolar ones.

i) diethyl-ether, benzene, n-hexane.

ii) acetone, acetamide, dichloroethane

iii) acetic acid, isopropanol, catechin

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