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The primary objective of this experiment is to familiarize with the use of an infrared spectrophotometer. In this experiment, we are to examine the spectra regions of solid and liquid samples.

Extracts from this document...

Introduction

Name: Neo Qing Hao

Class: DBT/2B/21

Admission No. : 0208725

Date of Experiment: 20 August 2003

Basic Instrumental Analysis

(CP4009)

Experiment 5:

Infrared Spectroscopy

1. Synopsis

The primary objective of this experiment is to familiarize with the use of an infrared spectrophotometer. In this experiment, we are to examine the spectra regions of solid and liquid samples. Mull technique was used to prepare solid samples and Pellet technique was used to prepare liquid samples. The spectra bands are very important information as it allows chemists to differentiate different functional groups and the concentration of the sample can also be determined from it. By using the correlation chart, we can identify the functional groups. In the prospect of handling infrared spectrophotometer, the most important part will be the sample cells. This is due to the sensitivity of the cells and the specificity of the types of cells.

2. Introduction

Infra-red spectroscopy originate from changes in the vibrational motion of atoms about their mean bond positions associated with the changes in the rotation of the molecule, thus it is also called vibration-rotation spectroscopy.

Infrared spectroscopy is a very useful technique used for the identification of functional groups in organic samples. The absorption peaks are sharper than in ultraviolet or visible regions, and thus easier to identify. Each and every molecule will have a different and unique spectrum, and this is tabulated in the correlation chart.

3. Theory

Basically infrared spectroscopy needs a few chemistry principles to work.

...read more.

Middle

image00.png

8) Steps (1) – (7) were repeated using fluorolube instead of paraffin oil

4.4 Determination of principal structures / functional groups of an unknown sample

1) The unknown sample was prepared using a suitable preparation method

image00.png

2) The spectrum was recorded

5. Results and Calculations

1) Results for calibration

Absorption band as indicated on polystyrene film (cmֿ¹)

Absorption band as indicated on chart paper (cmֿ¹)

3026

3025

2850

2849

1601

1601

907

907

2) Tables for procedures 4.2 and 4.3

N – hexane

image01.png

Pellet and the Liquid Cell Technique

Functional Group

Absorption Band (cm-1)

Identification Of Band

Alkane

2860, 2926, 2959

C-H stretching

Alkane

1459

C-H bending

Toluene

Pellet and the Liquid Cell Technique

Functional Group

Absorption Band (cm-1)

Identification Of Band

Alkane

2868, 2920

C-H stretching

Aromatic

694, 727

C-H out-of-plane vibration

Aromatic

1603

Ring vibration

Aromatic

1603

Substituents of ring

Aromatic

3027, 3059

Unsaturated C-H stretch

Methyl Ethyl Ketone

image02.png

Pellet and the Liquid Cell Technique

Functional Group

Absorption Band (cm-1)

Identification Of Band

Alkane

2940, 2980

C-H stretching

Alkane

1418

C-H bending

-C=O

1173

C-O stretching

-C=O

1717

C=O stretching

N – butanol

image03.png

Pellet and the Liquid Cell Technique

Functional Group

Absorption Band (cm-1)

Identification Of Band

Alkane

2872, 2957

C-H stretching

Alkane

1379

C-H bending

OH

1042, 1070, 1113

C-OH stretching

OH

3344

-O-H stretching

Sec – butanol

image04.png

Pellet and the Liquid Cell Technique

Functional Group

Absorption Band (cm-1)

Identification Of Band

Alkane

2879, 2828, 2967

C-H stretching

Alkane

1414

C-H bending

OH

1031, 1109, 1147

C-OH stretching

OH

3345, 3358

-O-H stretching

...read more.

Conclusion

" class="c24">

Carbon tetrachloride

image05.png

Pellet and the Liquid Cell Technique

Functional Group

Absorption Band (cm-1)

Identification Of Band

C-Cl

762

Chloride C-Cl stretch

Benzoic Acid

image06.png

Mull Technique

Functional Group

Absorption Band (cm-1)

Identification Of Band

Aromatic

1689

Substituents at ring

8. References

Infrared spectroscopy, website: http://www.organicworldwide.net/infrared.html

[Accessed 29 August 2003]

Characteristic IR Band Positions, website: http://infrared.als.lbl.gov/IRbands.html

[Accessed 29 August 2003]

Molecular Vibrations and IR Spectroscopy, website: http://academic.pg.cc.md.us/~ssinex/IR_spect.ppt

[Accessed 30 August 2003]

Infrared spectroscopy, website:

http://www.cem.msu.edu/~reusch/VirtualText/Spectrpy/InfraRed/infrared.htm

[Accessed 30 August 2003]

9. Appendix

Characteristic IR Band Positions

Group

Frequency Range (cm-1)

OH stretching vibrations

  Free OH

3610-3645 (sharp)

  Intramolecular H bonds

3450-3600 (sharp)

  Intermolecular H Bonds

3200-3550 (broad)

  Chelate Compounds

2500-3200 (very broad)

NH Stretching vibrations

  Free NH

3300-3500

  H bonded NH

3070-3350

CH Stretching vibrations

  =-C-H

3280-3340

  =C-H

3000-3100

  C-CH3

2862-2882, 2652-2972

  O-CH3

2815-2832

  N-CH3 (aromatic)

2810-2820

  N-CH3 (aliphatic)

2780-2805

  CH2

2843-2863,2916-2936

  CH

2880-2900

SH Stretching Vibrations

  Free SH

2550-2600

C=-N Stretching Vibrations

  Nonconjugated

2240-2260

  Conjugated

2215-2240

C=-C Stretching Vibrations

  C=-CH (terminal)

2100-2140

  C-C=-C-C

2190-2260

  C-C=-C-C=-CH

2040-2200

C=O Stretching Vibrations

  Nonconjugated

1700-1900

  Conjugated

1590-1750

  Amides

~1650

C=C Sretching Vibrations

  Nonconjugated

1620-1680

  Conjugated

1585-1625

CH Bending Vibrations

  CH2

1405-1465

  CH3

1355-1395, 1430-1470

C-O-C Vibrations in Esters

  Formates

~1175

  Acetates

~1240, 1010-1040

  Benzoates

~1275

C-OH Stretching Vibrations

  Secondary Cyclic Alcohols

990-1060

CH out-of-plane bending vibrations

   in substituted ethylenic systems

  -CH=CH2

905-915, 985-995

  -CH=CH-(cis)

650-750

  -CH=CH-(trans)

960-970

  C=CH2

885-895

...read more.

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