1. Beginning our final portfolio work
Carry out experiments on known organic functional groups to gain an understanding of what constitutes a positive result.
Explain the principle of the tests for a range of aliphatic functional groups (4.1)
Carry out a further experiment with unknown organic compounds to Identify a series of colourless organic liquids
Explain the absorbance of infra-red radiation in terms of covalent bond vibrations (5.1)
Interpret Infra-red and NMR spectra (5.2) of the organic compounds you investigated, annotating major absorbances/peaks that enable you to classify the compounds.

2. Spectroscopy
Spectroscopy is the study of the interaction between matter and electromagnetic radiation. 

3. Electromagnetic waves are waves that contain an  electric field and a magnetic field and carry energy. They travel at the speed of light.

4. Electromagnetic spectrum
Our spectrophotometers cover approx 300 – 800 nanometers so they just cover the beginning of uv and ir wavelengths
RSC animation shows what energies are picked up at different wavelengths

5. Spectroscopy visited
We have already used spectroscopy in our experiments and used a machine called Spectrophotometer.
In chemistry, spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material at different wavelengths.
spectrophotometry deals with visible light, near-ultraviolet, and near-infrared.

6. The UV – Visible spectroscopy
Routinely used for analysing coloured and colourless liquids in the UV and visible regions of the electromagnetic spectrum.
QUALITATIVE analysis
QUANTITATIVE analysis
Identify an UNKNOWN COMPOUND above 1500 cm-1 functional groups
Below 1500 cm-1 fingerprint region
You have used the spectrophotometer to Quantitatively analyse the concentration of copper sulphate and Qualitatively to look at the absorption spectrum of chlorophyll.
CONCENTRATION of a solution
PHOTOSPECTROMETER
INFRARED SPECTROMETER

7. Infrared spectroscopy is qualitatively used to identify organic compounds
IR spectroscopy provides a 100% identification if the spectrum is matched.
If not, IR at least provides information about the types of bonds present.

8. Infrared Spectroscopy
Infrared Group Analysis
Generally, the four primary regions of the IR spectrum
Bonds to H
O-H single bond
N-H single bond
C-H single bond
Triple bonds
C≡C
C≡N
Double bonds
C=O
C=N
C=C
Single Bonds
C-C
C-N
C-O
Fingerprint
Region
4000 cm-1
2700 cm-1
2000 cm-1
1600 cm-1
400 cm-1

9. Infrared Spectroscopy
Specific groups
Alkanes – combination of C-C and C-H bonds
Show various C-C stretches and bends between cm-1 (m)
Show C-H between cm-1 (s) cm -1

10. n-pentane 2850-2960 cm-1 CH3CH2CH2CH2CH3 sat’d C-H 3000 cm-1
alkane
1470 &1375 cm-1
CH3CH2CH2CH2CH3

11. Infrared Spectroscopy
Specific groups
Alkenes –
C=C stretch occurs at cm-1
vinyl C-H stretch occurs at cm-1
Note that the bonds of alkane are still present!
The difference between alkane and alkene C-H is important! If the band is slightly above 3000 it is vinyl C-H or below if its alkane C-H bonds

12. 1-decene 3020-3080 cm-1 C=C 1640-1680 unsat’d C-H
& RCH=CH2
C=C
alkene

13. Infrared Spectroscopy
Specific groups
Alcohols
Show a strong, broad band for the O-H stretch from cm-1 (s, br) this is one of the most recognizable IR bands
a band for C-O stretch between cm-1 (s)
The shape is due to the presence of hydrogen bonding
1-butanol

14. 1-butanol
(b) O-H
Primary alcohol
C-O 1o
CH3CH2CH2CH2-OH

15. Cyclohexyl carboxaldehyde
Infrared Spectroscopy
Specific groups
Aldehydes
Show the C=O (carbonyl) stretch from cm-1(s)
Also displays a highly unique C-H stretch as a doublet, 2720 & 2820 cm-1 (w) called a “Fermi doublet”
Cyclohexyl carboxaldehyde

17. Infrared Spectroscopy
Specific groups
Ketones
Simplest of the carbonyl compounds as far as IR spectrum – carbonyl only
C=O stretch occurs at cm-1 (s)
3-methyl-2-pentanone

19. ketone
What is the compound?
Aldehyde or ketone
ketone

20. Infrared Spectroscopy
Specific groups
Carboxylic Acids:
Gives the messiest of IR spectra
C=O band occurs between cm-1
The O-H bond has a broad band from cm-1 (m, br) covering up to half the IR spectrum in some cases
4-phenylbutyric acid

21. Ethanoic acid

23. Infrared Spectroscopy
Specific groups
Amines - Primary
Shows the –N-H stretch for NH2 as a doublet between cm-1 (s-m);
-NH2 group shows a deformation band from cm-1 (w)
2-aminopentane

24. ethylamine

25. Infrared Spectroscopy
Specific groups
Amides
C=O stretch occurs from cm-1
If the amide is primary (-NH2) the N-H stretch occurs from cm-1 as a doublet I
pivalamide

26. methanamide