This document provides an overview of spectroscopy techniques, including UV spectroscopy and mass spectroscopy. It discusses the different types of electronic transitions that can occur when electromagnetic radiation interacts with matter, such as σ→σ*, n→σ*, π→π*, and n→π* transitions. It also explains Beer's law and how it relates absorbance to characteristics of the absorbing substance. Additionally, it describes the components and basic principles of UV-Vis spectrometers and mass spectrometers, and provides some examples of applications for these techniques.

1. BY
HEMA MALINI.S
2017694709
SPECTROSCOPY

2. INTRODUCTION
 Spectroscopy –study of interaction between of
electromagnetic radiation with matter

3.  There are two ways of interaction between
electromagnetic radiation and matter can takes place

4. ELECTRO MAGNETIC RADIATION

5. UV SPECTROSCOPY
 It is also known as electronic spectroscopy.
 Uv ranges from 190-400nm
 Valence electrons absorb the energy thereby molecules
undergoes transition from ground state to excited state.

6. BEER –LAMBERT LAW:
 This law states that amount of light absorbed is directly
proportional to the concentration of absorbing substance and to
thickness of absorbing material.
A = abc or log(Iₒ/I) =abc
Where
A is absorbance
b is path length (cm)
c is concentration (M)
a is molar absorptivity constant(1/Mcm)
Molar absorptivity is the charateristic of a substance that tells how
much of light is absorbed at a particular wave length.

9. σ→ σ⃰
 σ electron from bonding orbital is excited to corresponding
antibonding orbital σ⃰ .
 The energy require is large for the transition.
 The organic compounds in which all the valence shell electron
are involved in the formation of σ bond do not show absorption
in uv region.
 This transition is observed with saturated compounds
 Eg :Methane has C-H bond only and can undergo σ- σ⃰ transistion
and shows absorption maxima at122 nm.
 The usual spectroscopic technique cannot be used below 200 nm.
 To study this high energy transition the entire region should be
evacuated
 Here, the excitation occurs with net retention of electronic spin.
 This region is less informative.

10. n→σ⃰
 Saturated compounds containing one hetero atom with
unshared pair of electrons like O,N,S and halogen
capable of n→σ⃰ transitions
 These transiton require low energy than σ→ σ⃰
transitions.
 Eg methyl chloride.

11. π→π⃰
 π electron in a bonding orbital is excited to
corresponding antibonding orbital π⃰.
 Energy required is less when compared to n- σ⃰
 Compounds containing multiple bonds like
alkenes,alkynes,carbonyls,nitiriles,aromatic componds.
etc undergo π→π⃰ transitions.
 Absorption usually occurs in the normal uv
spectrophotometer.

12. n→π⃰
 An electron from non bonding electron is promoted to
antibonding π⃰ orbital .
 Compounds containing double bonds involve in hetero
atom (C=O,N=O) undergo such transition.
 The transition requires minimal energy

14. Uv-vis spectrometer

15. Case study

16. Application
 Detection of impurities.
 Qualitative analysis.
 Quantitative analysis.

17. Mass spectroscopy
 Mass spectrometry is an instrumental technique in
which sample is converted to rapidly moving positive
ion by electron bombardment and charged particles are
separated according to their masses.
 It measures the molecular weight of compound by the
ratio of mass to charge

18. Simple mass spectroscopy

19. Basic principles of MS

21. COMPONENTS OF MS

22. INSTRUMENTATION

23. Application
 Used in the field of proteomics.
 Used in phytochemical screening of unknown
compound .
 Used in detection of pesticides in food .
 Used in pharmaceutical analysis.