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UV-VISIBLE RANGE, ENERGY,

WAVELENGTH AND COLORRELATIONSHIP

PRESENTED BY:

CHIRAG DARJI

1STM.PHARM

PHARMACOLOGY DEPT.

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CONTENTS

Spectroscopy

Visible spectroscopy

UV-Spectroscopy UV-Visible range

Energy

Wavelength and Color Relationship

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SPECTROSCOPY

Measurement and interpretation of electro-magnetic radiation absorbed or emitted.

Spectroscopy measures the changes inrotational, vibrational and/or electronicenergies.

ETOTAL =EROTATIONAL +EVIBRATIONAL + EELECTRONIC

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ROTATIONAL ENERGY

Also known as a angular kinetic energy.

Associated with the overall rotation of themolecule with the atoms consider as a fixed

point masses. Occurs in microwave region.

EROTATION = I wwhere

w is the angular velocityI is the moment of inertia.

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VIBRATIONAL ENERGY

A molecule can also acquire energy as aresult of vibrations in the molecules.

Occurs in infra red region.

EVIBRATIONAL = hv0( v + )

Where, Vo = Natural frequency of vibrationV = Vibrational quantum number

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ELECTRONIC ENERGY

Associated with the transition of an electronfrom the ground state energy level to an excitedstate energy level of the molecule because of

absorption of photon of suitable frequency.

Occurs in UV visible region.

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VISIBLE SPECTROSCOPY

Also known as visual spectroscopy orcolorimetry.

Colorimetry is concerned with the study ofabsorption of visible radiation.

WAVELENGTH400 nm800nm

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UV ( ULTRA VIOLET ) SPECTROSCOPY

Concern with the study of absorption of UV-radiation .

WAVELENGTH 200 nm400 nm

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ENERGY

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The energy of the radiation depends uponthe frequency and wavelength of the

radiation.

Frequency is directly proportional to the

energy, but as the energy increases, thewavelength decreases.

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Types of electrons present in any

molecule:

1. s Electrons: Present in saturated compounds.

E.g. - Alkanes

2. p Electrons: Present in unsaturated compounds.E.g.double or triple bonds

3. n Electrons: Non bonded electrons which arenot involved in any bonding.

E.g. lone pair of electrons.

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Sigma and Pi orbitals

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Types of electronic transition in organic compounds:

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Change in energy values for different transitionare in following order :

n* < * < n*< *

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n* TRANSITION

Also occurs in as conjugates dines.

Shows by unsaturated molecules which containoxygen, nitrogen and sulphur.

Requires less energy.

ExampleAldehyde and ketones.

Range270nm300nm

( 2700 -3000 A.

)

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*TRANSITION

Gives promotion of an electron from a bonding orbital to an antibonding*orbital.

Mainly occurs in molecules having a electron

system.

Example Alkenes

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n* TRANSITION

Saturated compounds with lone pair of electron

undergo n* transition.

Less energy required compare to the *.

Range 180nm-200nm (Near UV)

Some compound absorb at slightly longerwavelength. For example-

(CH3)3N, max = 227nm for n* Hydrogen bonding shifts the UV absorption to

shorter wavelength.

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* TRANSITION

Occurs in compounds in which electron areinvolved in single bonds and no lone pairs ofelectron.

Requires highest energy.Absorption band occurs in UV at range 126nm-

135nm.

Examples : AlkanesSaturated Hydrocarbon

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WAVELENGTH

Distance between two successive maxima or minima ORDistance between two successive troughs or peaks.

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QUANTITY RELATIONSHIP UNITS

Wavelength = 1/v = c/v m, m, nm

Wave Number = 1/ = v/c m-1

, cm-1

Frequency V = c/ = c S-1, (HZ)

Velocity c = v = v/ ms-1

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Frequency :

No. of the complete wavelength unitspassing through a given point in a unit time.

Wavenumber:

No. of the waves spread in a length of one

cm.

Velocity:Distance travelled by the wave in one second.

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COLOR RELATIONSHIP

Violet: 400 - 420 nm Indigo: 420 - 440 nm

Blue: 440 - 490 nm

Green: 490 - 570 nm

Yellow: 570 - 585 nm Orange: 585 - 620 nm

Red: 620 - 780 nm

Red has the longest wavelength.

Violet has the shortest wavelength.

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REFERENCES

ORGANIC SPECTROSCOPY

BY : William Kemp

INSTUMENTAL METHODS OF CHEMICAL ANALYSIS

BY : G.R.Chatwal, S.K.Anand

INSTUMENTAL METHODS OF CHEMICAL ANALYSIS

BY : B.K.Sharma

PHARMACEUTICAL DRUG ANALYSIS

BY : Ashutosh Kar

www.google.com

en.wikipedia.org

http://www.google.com/http://www.google.com/

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