Ir

1,256 views
996 views

Published on

Published in: Technology, Business
1 Comment
0 Likes
Statistics
Notes
  • Be the first to like this

No Downloads
Views
Total views
1,256
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
82
Comments
1
Likes
0
Embeds 0
No embeds

No notes for slide

Ir

  1. 1. Presenter-Presenter- Naveen KadianNaveen Kadian 1
  2. 2.  Introduction  Principle  Instrumentation  Sample Handling  Interpretation  Applications 2
  3. 3. • What is Spectroscopy? Technique that uses the interaction of energy from radiations with a sample to perform an analysis. 3 • Terms Associated with IR Spectroscopy- • Transmittance • Wave number • Requirement for IR Spectroscopy- • Correct Wavelength of Radiation • Electric Dipole • Planck Constant λν hchE == IR Spectroscopy: NEAR INFRARED: 0.8 -2.5 µm, 12500 - 4000 cm-1 MID INFRARED: 2.5 - 25 µm, 4000 - 400 cm-1 FAR INFRARED: 25 - 1000 µm, 400 - 10 cm-1
  4. 4. http://upload.wikimedia.org/wikipedia/en/8/8a/Electromagnetic-Spectrum.png e- Bond breaking and ionization Electronic excitation Vibration Rotation
  5. 5.  Infrared radiation stimulates molecular vibrations  Types of Molecular Vibrations › Stretching › Bending  In-Plane Deformations  Out-Plane Deformations 5
  6. 6.  Factor effecting Vibrations:  Fermi Resonance  Resonance causing the transfer of energy from fundamental to overtone and vice-versa  helps in explaining the doublet  Electronic Effects  electro+ve +I effect decrease wavenumber  Electro -ve -I effect increases wavenumber  Hydrogen Bonding  stronger the hydrogen bonding greater the absorption shift towards lower wavenumber  Intramolecular Bonding give sharp peaks whereas Intermolecular Bonding give Broad peaks which is concentration dependant 6 • Stretching frequencies are higher than corresponding bending frequencies. • Triple bonds have higher stretching frequencies than corresponding double bonds, which in turn have higher frequencies than single bonds.
  7. 7. 7 • Instrumentation of IR Spectrophotometer mainly consists of: • Source • Monochromators • Sample Cells • Detector • Sources: A hot material emits a continuum of radiation. Blackbody (no envelope): intensity highest near 5000 cm-1 ; about 100 times lower near 500 cm-1 . a. Nichrome coil heated electrically to 1100o C and a black oxide film forms. Simple, robust, reliable, long lifetime.
  8. 8. 8 b) Nernst glower aux. heater 2 - 5 cm Has - temp coefficient. of resistance. 1 - 3 mm dia. ceramic holder Y2O3, ThO2, ZrO2 heated up to 1500oC Pt leads cement
  9. 9.  Monochromators: › Prism Monochromators:  used for the selection of radiation of desired Frequencies  made up of NaCl due to its high Dispersion in the range of 4 to 15µm › Grating Monochromators:  higher dispersion  mainly of Aluminum  Sampling Techniques: › For Solids  Solid Film  Solid run in Solution  Mull Technique  Pressed Pellet Technique 9
  10. 10. › For Liquids  Sample is Sandwitched Between Alkyl Halides › For Gases  The path length is 10 cms and plain tubular endings are supplied as standard 10
  11. 11.  Detectors:  Golay cell  Pyroelectric Detector 11 Change in detector temp. by IR absorption changes lattice spacing and polarization – charge moves. Fast response time: 1µs-1ms Ignore steady background
  12. 12.  Photon Detector  Semiconductor Detector 12
  13. 13. 13
  14. 14.  Fourier Transform Infrared (FT-IR) spectrometry was developed in order to overcome the limitations encountered with dispersive instruments. › Ability to measure all wavelength simultaneously rather then individually.  The interferometer produces a unique type of signal which has all of the infrared frequencies “encoded” into it.  Beamsplitter  Interferogram  Fourier transformation. 14
  15. 15. 15
  16. 16.  Some of the major advantages of FT-IR over the dispersive technique include: › Speed › Sensitivity › Mechanical Simplicity › Internally Calibrated: These instruments employ a HeNe laser as an internal wavelength calibration standard 16
  17. 17. Typical Infrared AbsorptionTypical Infrared Absorption RegionsRegions 4000 2500 2000 1800 1650 1550 650 FREQUENCY (cm-1 ) WAVELENGTH (µm) O-H C-H N-H C=O C=N Very few bands C=C C-Cl C-O C-N C-CX=C=Y (C,O,N,S) C N C C N=O N=O*
  18. 18. •C-H aldehyde, two peaks (both weak) ~ 2850 and 2750 cm-1 3000 divides UNSATURATED SATURATED •C-H sp stretch ~ 3300 cm-1 •C-H sp2 stretch > 3000 cm-1 •C-H sp3 stretch < 3000 cm-1 The C-H stretching region BASE VALUE = 3000 cm-1 THE C-H BENDING REGIONTHE C-H BENDING REGION CH2 bending ~ 1465 cm-1 CH3 bending (asym) appears near the CH2 value ~ 1460 cm-1 CH3 bending (sym) ~ 1375 cm-1
  19. 19. CH3CH2 1465 1460 1375 asym sym METHYLENE AND METHYL BENDING VIBRATIONSMETHYLENE AND METHYL BENDING VIBRATIONS these two peaks frequently overlap and are not resolved C-H Bending, look near 1465 and 1375 cm-1 C H H H
  20. 20. CH3CH2 1465 1460 1375 asym sym 13701380 13701390 C CH3 CH3 C CH3 CH3 CH3 C CH3 METHYLENE AND METHYL BENDING VIBRATIONSMETHYLENE AND METHYL BENDING VIBRATIONS geminal dimethyl t-butyl (isopropyl) two peaks two peaks The sym methyl peak splits when you have more than one CH3 attached to a carbon. ADDITIONAL DETAILS FOR SYM CH3 one peak
  21. 21.  O-H 3600 cm-1 (alcohol, free)  O-H 3300 cm-1 (alcohols & acids, H-bonding) 3600 3300 H-BONDED FREE broadens shifts N-H 3300 - 3400 cm-1  Primary amines give two peaks  Secondary amines give one peak  Tertiary amines give no peak N H H N H Hsymmetric asymmetric
  22. 22.  C N 2250 cm-1  C C 2150 cm-1 = == = The cyano group often gives a strong, sharp peak due to its large dipole moment. The carbon-carbon triple bond gives a sharp peak, but it is often weak due to a lack of a dipole. This is especially true if it is at the center of a symmetric molecule. R C C R
  23. 23. 1810 and 1760 acid chloride ester aldehyde carboxylic acid amideketone CR O H CR O O C R O CR O Cl CR O OR' CR O R CR O NH2 CR O OH ( two peaks ) HOW THE FACTORS AFFECT C=OHOW THE FACTORS AFFECT C=O STRETCHING VIBRATIONS B A C D A B D CE-donating E-withdrawing Resonance H-bonding 1800 1735 1725 1715 1710 1690 BASE VALUE anhydride
  24. 24.  Conjugation of a carbonyl with a C=C bond shifts values to lower frequencies  For aldehydes, ketones and esters, subtract about 25-30 cm-1 for conjugation with C=O  Conjugated ketone = 1690 to 1680 cm-1  Conjugated ester = 1710 to 1700 cm-1 • The C-O band appears in the range of 1300 to 1000 cm-1 •Look for one or more strong bands appearing in this range!
  25. 25.  N=O stretching -- 1550 and 1350 cm-1 asymmetric and symmetric stretching.  Often the 1550 cm-1 peak is stronger than the other one. The C-X stretching region • C-Cl 785 to 540 cm-1 , often hard to find amongst the fingerprint bands!! • C-Br and C-I appear outside the useful range of infrared spectroscopy. • C-F bonds can be found easily, but are not that common.
  26. 26. C=O present ? 2 C=O Peaks OH present ? NH present ? C-O present ? CHO present ? anhydride acid amide ester aldehyde ketone YES YES NO
  27. 27. C=O present ? OH present ? NH present ? C-O present ? C=N present ? C=C present ? C=C present ? alcohol amine ether nitrile alkyne alkene aromatic NO2 present ? nitro cpds C-X present ? halides (benzene ?) NO YES = =
  28. 28. C=O present ? 2 C=O Peaks OH present ? OH present ? NH present ? NH present ? C-O present ? C-O present ? CHO present ? C=N present ? C=C present ? C=C present ? anhydride acid amide ester aldehyde ketone alcohol amine ether nitrile alkyne alkene aromatic NO2 present ? nitro cpds C-X present ? halides (benzene ?) YES YES NO YES NO = =
  29. 29. acid THE MINIMUM YOU NEED TO KNOW OH 3600 NH 3400 CH 3000 C N 2250 C C 2150 C=O 1715 C=C 1650 C-O 1100 3300 3100 2900 2850 2750 3000 1800 1735 1725 1715 1710 1690 =C-H -C-H -CHO C-H ketone esteracid chloride aldehyde amide anhydride : 1810 and 1760 CH2 and CH3 bend : 1465 and 1365 BASE VALUES benzene C=C : between 1400 and 1600 EXPANDED CH EXPANDED C=O
  30. 30. 30
  31. 31. 31
  32. 32. 1. Determination of Functional Group of the unknown Substance 2. Identification of Substance 3. Determination of Molecular Weight 4. Studying the Progress of Reaction 5. Detection of Impurities 6. Determination of Purity 7. Forensic investigations 8. Polymer analysis 9. Foods research 10. Quality assurance and control 11. Environmental and water quality analysis methods 32 Application of IR Spectroscopy
  33. 33. 33 Refernces 1. Stuart Barbara; “Infrared Spectroscopy: Fundamentals and Principles”; Wiley Publications. 2. William Kemp; “Organic Spectroscopy”; 3rd edition; 1991; McMillan Publishers. 3. Cross A.D. and Jones R. Alan; “An Introduction to Practical Infrared Spectroscopy”; 3rd edition; Butterworth and Co. Publishers Ltd. 4. Galen W. Ewing; “Instrumental methods of chemical analysis”; 5th edition; 1985; McGraw Hill Book Company.
  34. 34. 34 ‘Success is the ability to go from failure to failure without losing our enthusiasm’ Thank you

×