INFRARED SPECTROSCOPY
description
Transcript of INFRARED SPECTROSCOPY
![Page 1: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/1.jpg)
INFRAREDSPECTROSCOPY
![Page 2: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/2.jpg)
INFRAREDSPECTROSCOPY
the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light.
![Page 3: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/3.jpg)
INFRARED OFELECTROMAGNETIC SPECTRUM
Near-infrared
Mid-infrared
Far-infrared
http://www.nasa.gov/images/content/56638main_Infrared_Region.jpg
![Page 4: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/4.jpg)
NEAR-INFRAREDapproximately 14000-4000 cm−1 (0.8–2.5 μm wavelength) Can excite overtone or harmonic vibrations.Has high energy
![Page 5: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/5.jpg)
MID-INFRARED approximately 4000-400 cm−1 (2.5–25 μm) used to study the fundamental vibrations and associated rotational-vibrational structure.
![Page 6: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/6.jpg)
approximately 400–10 cm−1 (25–1000 μm)
lying adjacent to the microwave regionhas low energy and may be used for rotational spectroscopy.
FAR-INFRARED
![Page 7: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/7.jpg)
2.5x10-6 to 2.5x10-5 mVibrational infared region – the portion of the infrared region that extends from 4000 to 400 cm-1
Wavenumber (v) – radiation in the vibrational infrared region. The number of waves per centimeter.
THE VIBRATIONAL INFRARED SPECTRUM
![Page 8: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/8.jpg)
Atoms joined by covalent bonds are not permanently fixed in one position, but instead undergo continual vibrations relative to each otherThe bond undergoing vibration must be polar. It’s vibration must cause a periodic change in the bond dipole.The greater the polarity of the bond, the more intense is the absorption.
MOLECULAR VIBRATIONS
![Page 9: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/9.jpg)
3n – 6 (fundamental vibrations)
Example:Ethanol CH3CH2OHHexanoic acid CH3(CH2)4COOH
![Page 10: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/10.jpg)
STRETCHING MOTIONS
Change in band length
Symmetrical stretching
Assymmetric stretching
![Page 11: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/11.jpg)
• Change in band angle.BENDING MOTIONS
Scissoring
Rocking
Twisting
Wagging
![Page 12: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/12.jpg)
Data on absorption patterns of selected functional groups are collected.
CORRELATION TABLES
Characteristic IR Absorptions of Selected Functional GroupsBond Frequency (cm-1) Intensity O-H 3200-3500 Strong and broad
N-H 3100-3500 Medium
C-H 2850-3100 Medium to strong
C≡C 2100-2260 Weak
C=O 1630-1800 Strong
C=C 1600-1680 Weak
C-O 1050-1250 Strong
![Page 13: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/13.jpg)
Example:Determine the functional group that is likely present if a compound shown IR absorption at
1705 cm-1
2950 cm-1
![Page 14: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/14.jpg)
FACTS absorption of IR radiation only occurs if there is a change in dipole moment the larger the change in dipole moment, the more intense the absorption band the greater the electronegativity differences between atoms in the molecule, the more polarized, the larger change in dipole moment
![Page 15: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/15.jpg)
INTERPRETINGINFRAREDSPECTRA
![Page 16: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/16.jpg)
INFRARED SPECTRUMTr
ansm
itta
nce
Wavenumber (cm-1)
![Page 17: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/17.jpg)
ALKANES
decane
![Page 18: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/18.jpg)
ALKENES
cyclopentene
![Page 19: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/19.jpg)
ALKYNES
1-octyne
![Page 20: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/20.jpg)
ARENES
toluene
![Page 21: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/21.jpg)
ALCOHOLS
2-pentanol
![Page 22: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/22.jpg)
ETHERS
Diethyl ether
![Page 23: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/23.jpg)
KETONES
menthone
![Page 24: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/24.jpg)
AMINES
butanamine
![Page 25: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/25.jpg)
AMIDES
N,N-dimethyldodecanamide
![Page 26: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/26.jpg)
AMIDES
N-methylbenzamide
![Page 27: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/27.jpg)
AMIDES
butanamide
![Page 28: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/28.jpg)
CARBOXYLIC ACIDS
Butanoic acid
![Page 29: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/29.jpg)
ESTERS
Ethyl butanoate
![Page 30: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/30.jpg)
INDEX OF HYDROGEN DEFICIENCY
The sum of the number of rings and pi bonds in a molecule.Compare the number of hydrogens in the molecular formula of a compound of unknown structure with the number of hydrogen in a reference compound with the same number of carbon atoms and with no rings or pi bonds.
![Page 31: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/31.jpg)
CnH2n+2
Index of Hydrogen = (Hreference – Hmolecule)
2
![Page 32: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/32.jpg)
Example
Index of hydrogen deficiency = 4
![Page 33: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/33.jpg)
UV-VISSPECTROSCOPY
Ultraviolet-visible Spectroscopy
![Page 34: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/34.jpg)
Measures the attenuation of a beam of light after it passes through a sample or after reflection from a sample surface. Spectral range of 190 nm to 900 nm
190 – 400 nm, UV 400 – 750 nm, Vis
UV-VIS SPECTROSCOPY
![Page 35: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/35.jpg)
ELECTRONIC TRANSITION
Vis = 36 – 72 kcal/mol UV = >72 – 143kcal/mol
![Page 36: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/36.jpg)
CHROMOPHORE• identifiable part of the molecule• responsible for any spectral feature like bands• use to deduce presence of structural fragment
or element in the molecule• corresponds to a functional group, an atom or
group of atoms• Molar absorptivity > 200 for UV-Vis
![Page 37: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/37.jpg)
UV-VIS SPECTRUM
• UV - electronic transition in 200 – 380 nm• Vis - electronic transition in 380 – 800 nm
![Page 38: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/38.jpg)
EFFECTS OF CONJUGATION
![Page 39: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/39.jpg)
EFFECTS OF CONJUGATION
![Page 40: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/40.jpg)
SCHEMATIC OF A WAVELENGTH-SELECTABLE, SINGLE-BEAM UV-
VIS SPECTROPHOTOMETER
![Page 41: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/41.jpg)
UV-VIS SPECTROPHOTOMETER
![Page 42: INFRARED SPECTROSCOPY](https://reader036.fdocuments.in/reader036/viewer/2022081722/56816011550346895dcf13c1/html5/thumbnails/42.jpg)
References• http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htm
Thank You!