Seminar of Chirag
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Transcript of Seminar of Chirag
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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
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