Full Report Uv-Vis and Ftir

ABSTRACT

In this experiment we are going to identify organic compounds by using UV-Vis and IR Spectroscopy. The purpose of this experiment is to provide an opportunity to implement the skills have gained from the first two chapters of the Instrumental Chemistry course. We will identify 12 compounds (A-L) using knowledge of UV-Vis and IR Spectroscopy. The experiment was conducted by testing 6 unknown compounds by using UV-Vis and IR Spectroscopy. Each compounds has different value of frequency range, by comparing the data we get from experiment with information given by lecturer all the compounds can be determined. The unknown compounds are A = Ethanol, C = Ethanoic Acid, D = Ethyl Ethanoate, I = Benzoic Acid, J = Ethyl Bromide and K = Diethyl Ether. The experiment is successfully done with some errors that may influence the result.

INTRODUCTION

Ultraviolet Spectroscopy (UV-Vis)

Ultraviolet (UV) was discovered more than 200 years ago by Johann Ritter. In 1801, he reported in Annalen de Physik that, on the 22nd February, he had detected solar radiation. This is referring to Oldenburg and Eden in the Ultraviolet Spectroscopy and UV Lasers.

According to John and Stephen, the infrared portion of the electromagnetic spectrums spans from about 3.8x1014 Hz to 6 x1012 Hz. If the sample is illuminate by radiation of a particular and discrete wavelength, then absorption of that radiation might occur. Most of the common functional group absorbs IR radiation within the range 200 780 nm. At other wavelength the radiation might not occur.

Figure 1: Lambda 750 UV/Vis/NIR Spectrophotometer (Annon, 2013)

In this experiment, the Lambda 750 UV/Vis/NIR Spectrophotometer is designed to give highest sampling flexibility especially it is commonly use in Chemistry, Forensic and Applied Science field. This system is suitable for research or teaching laboratory, as accessories and detector modules can quick and easily interchanged to provide the optimum configuration for each measurement. This instrument also maintains critical performance at the highest level.

The main purpose of this instrument is to analyze compounds in the ultraviolet and visible regions of electromagnetic spectrum. The degree of conjugated double or triple bonds and degree of aromaticity is the structure of binders which are evaluated by using UV-Vis spectroscopy reported by Mills and George D. The UV radiation is passed through the sample and absorption radiation occurs. The radiation transmitted is detected by photocells and the spectrometer records the absorption by comparing the difference between the intensity of the radiation passing through and the reference cells. Nowadays, the UV-Vis spectroscopy is being upgraded to give better results and expanding the potentials of the UV-Vis field.

IR Spectroscopy

Fourier Transform Infrared or known as FTIR is a method of infrared spectroscopy that can be used to identify chemicals that are either organic or inorganic and also can be used on solids, liquids, and gases. It also can measure all the Infrared (IR) wavelengths simultaneously which this feature is called the Multiplex or Felgett Advantage and produces a full spectrum. Simply, it can absorb different measurement of the IR frequencies by positioned a sample in the path of an IR beam.

Figure 2: Perkin Elmer FTIR Spectrum 100

In this experiment, the Perkin Elmer FTIR Spectrum 100 is used this instrument provides the highest quality lab experience, along with the most accurate and reproducible results in the industry.

The main objective of the FTIR spectroscopic analysis is to identify of compounds by matching spectrum of unknown compound with reference spectrum (finger printing). Moreover, it also can be used to detect functional groups in unknown substances.

In addition, this spectroscopy can produce an infrared absorption spectrum that is like a molecular "fingerprint" to identify the types of chemical bonds in a molecule. Just like the fingerprint, no two unique molecular structures can produce the same infrared spectrum so this will make the infrared spectroscopy useful for several types of analysis.

AIMS

In this experiment, we are going to

1. Identify organic compounds with are A, C, D, I, J and K by using UV-Vis and IR Spectroscopy.

THEORYThe ultraviolet-visible (UV-Vis) spectrophotometer is an instrument commonly used in the laboratory to analyze compounds in the ultraviolet (UV) and (Vis) regions of the electromagnetic spectrum. The wavelength of UV is from 200 380 nm while wavelengths for the UV-Vis are fall between 200 and 780 nm. It is known that, the shorter the wavelength, the higher the energy.

The UV-Vis spectroscopy works by looking at the electrons transition. The electrons transitions of a compound can determine the wavelength and the maximum absorbance of compounds. The UV or visible radiation is absorbed due to the excitation of the outer electrons. The electrons are promoted from their ground state to an excited state when an atom or molecule absorbs the energy. The atoms can rotate and vibrate with respect to each other in a molecule. The vibrations and rotations also have discrete energy levels, which can be said as being packed on top of each electronic level. The absorption of the ultraviolet and visible radiation in organic molecules is restricted to several functional groups (chromophores) which is contains valence electrons of low excitation energy. The spectrum of a molecule containing the chromophores is complex that is because the superposition of rotational and vibrational transitions gives a combination of overlapping lines on the electronic transitions. This will show as a continuous absorption band.

Figure 1: Possible electronic transitions of p, s, and n electrons

(( (*TransitionsThis transition is where the anti-bonding orbital is being excited by an electron in a bondingsorbital. The energy required is large. For example, methane (which has only C-H bond, and can only undergo( ( (*transitions) that shows an absorbance maximum at 125 nm.n( (*TransitionsThis transition is capable for the saturated compounds containing atoms with lone pairs (non-bonding electrons). These transitions usually need less energy than( ( (*transitions. The light whose have the wavelength that is in the range from 150 to 250 nm can only initiated this transition.

n( (*and( ( (*TransitionsThe transitions ofnorpelectrons to thep*excited state is the most absorption spectroscopy of organic compounds that being happened. It was been said like that because the absorption peaks for these transitions fall in an experimentally convenient region of the spectrum (200 - 700 nm). Other than that, these transitions also need an unsaturated group in the molecule to provide thepelectrons.

The core principle used behind the absorbance in this spectroscopy is Beer-Lambert Law (Equation1). For a single wavelength, the symbol of A is the absorbance (it is unitless and usually seen as arbitrary units), is for the molar absorptivity of the compound or molecule in solution (M-1cm-1), b is for the path length of the cuvette or sample holder (1 cm long), and c is the concentration of the solution (M).

A = bc

Equation (1)

However, the UV-Vis spectroscopy can identify the chromophores or known as functional group of the compound only. While fourier transform infrared spectroscopy (FT-IR) can identify the specific functional group for the sample of compound. The region where the specific chromofores can be detected is between 400 and 600 cm-1 .This FT-IR is a method of infrared spectroscopy that can be used to identify chemicals that are either organic or inorganic and also can be used on solids, liquids, and gases.

Modern instruments are FTIR spectrometer that obtains the IR spectrum by Fourier transformation of the signal from an interferometer with a moving mirror. (Sawyer et al., 2008). According to Gable (2013) the mathematical expression of Fourier transform can be expressed as

F() = And the reverse Fourier transform is

f(x) = Where is an angular frequency and x is the optical path difference in our case. F() is the spectrum and f(x) is called interferogram.

Figure 1.1 : Michelson interferometer experiment (Anon, 2006)

In a Michelson interferometer adapted for FTIR consists of

Stationary mirror

Moving mirror

Beamspitter

Detector

Sample

The working principle of Michelson Interferometer

1. Source of energy is send through an interferometer and onto the sample. All source radiation gets to the sample.

2. The light passes through a beamsplitter, which sends the light in two directions at right angles. One beam goes to a stationary mirror then back to the beamsplitter. The other goes to moving mirror.

3. The motion of the mirror makes the total path length variable versus that taken by the stationary-mirror beam. When the two meet up again at the beamsplitter, they recombine, but the difference path in path lengths creates constructive and destructive interference.

4. The recombined beam passes through the sample. The sample absorbs all the different wavelengths characteristic of its spectrum, and this subtracts specific wavelengths from the interferogram

5. The detector now reports variation in energy versus time for all wavelengths simultaneously.

6. A laser beam is superimposed to provide a reference for the instrument operation.

APPARATUS & CHEMICALS UV-Vis Spetrometer FT-IR Spectrometer

6 unknown compounds labelled as A, C, D, I, J, and K.

Dropper

PROCEDUREUV-Vis To Turn on the Equipment

1. The instrument is turned on. It took 5 minutes to warm up.

2. The software Perkin Elmer UV VIS/NIR is turned on.

3. Went to New and Method is clicked.

4. Type of instrument (high performance UV/VIS/NIR) is selected and clicked Next and the wavelength for the instruments is chosen.

5. Clicked Next and the method type is selected.

6. After that, scanned and clicked Next twice.

7. The method is saved and named. Then, clicked ok.To Create Method

1. Went to the data collection.

2. The wavelength is set depending to manual lab which is from 300 nm to 500 nm.

3. Went to ordinate mode and the Absorbance parameter is chosen.

4. Went to sample info then the quantity of sample is inserted, ENTER is pressed.

5. For the first sample, it was put as blank.

6. The sample ID is edited with A, C, D, I, J and K.

7. The wavelength is set for the experiment.

8. Clicked button start and then ok.

9. The sample holder is inserted with both blank sample which is contains ethanol. The fingerprints around the glass container where the sample is filled in.

10. Next, repeat steps 8 and 9 by replaced one of the ethanol sample with sample A, C, D, I, J and K.

11. For the sample of solid I, the sample is diluted first before placed in the sample holder.FTIR spectroscopy

1. 5 solutions of samples and 1 solid sample is prepared.

2. The computer is turned on. Clicked at software spectrum.

3. Clicked at the background and Ready for scan sample is appeared.

4. Clicked at instrument scan. The box is appeared where the information need to be key in.

5. Clicked at scan and the range to run the sample is inserted.

6. Apply is clicked and the sample is scanned when it is ready.

7. The top plate is cleaned with acetone.

8. If the sample is liquid, it is drop into hole of top plate.

9. If the sample is solid sample, it is inserted into hole and it is purged.

10. The first sample to be scanned is sample A.

11. The sample is scanned.

12. After the first sample, the top plate is cleaned with acetone.

13. Step 4 to 12 is repeated with other samples.

14. Every results is copied into Microsoft Excel.RESULTS IR SpectraCompound A

Compound C

Compound D

Compound J

Compound K

Compound I

UV-Vis Spectra Dr mikail Tuesday, March 26, 2013 3:20 PM Malay

Peninsula Standard Time

BLANK

Dr mikail Tuesday, March 26, 2013 3:20 PM Malay


A



C



D



I



J



K

FTIR analysis

Unknown compound (Sample)Band ( IR)

(cm-1)Descriptions Name of compound

and functional group

A3319.21

2973.13

2926.28

2881.99O-H stretch

C-H stretch

C-H stretch

C-H stretch Compound : Ethanol

presence of alcohol group.

C3039.82

2933.05

1756.99

1704.49O-H stretch

O-H stretch

C=O stretch

C=O stretch Compound : Acetic/ Ethanoic acid (CH3COOH)

presence of carboxylic acid group.

D2984.71

1736.53

1233.50

1043.58

C-H stretch

C=O stretch

C-O stretch

C-O stretch Compound : Ethyl ethanoate (CH3COOHCH2CH3)

presence of ester group.

I2988.99

1983.75

1682.51

O-H stretch

Aromatic C-H stretch

C=O stretch

Compound : Benzoic Acid

(C6H5COOH)

presence of aromatic ring and carboxylic acid group.

J2978.81

2924.17

2866.70

1241.01

559.05C-H stretch

C-H stretch

C-H stretch

C-H wag

C-Br stretch Compound : Ethyl bromide

presence of alkyl halide group.

K2976.37

2860.32

1118.25C-H stretch

C-H stretch

C-O-C stretch Compound : Diethyl ether

presence of ether group.

Uv-vis analysis

Compoundsmax (nm)Intensity (A)Absorptions occurrenceDescriptions

Blank00No-

A213.250.2338NoDouble bond absent

C214.090.856YesDouble bond present

D214.131.039YesDouble bond present

I215.113.173YesDouble bond present

J214.231.603NoDouble bond absent

K213.370.622NoDouble bond absent

DISCUSSION

In UV-Vis analysis, the blank that we used was water which has an approximately 180 nm cut-off wavelength. Cut off wavelength is the approximate wavelengths below which it cannot be used because the solvent itself absorbs all of the light (Skoog, et al., 2007). The cuvette bottle has a cut-off wavelength too which for glass and plastic were ranged between 380-780 nm (Barron, 2010). On the other hand, acetone is used for cleaning the cuvettes and the plate because it is more effective than water to remove the traces of any impurities and oily marks on the surfaces including the fingerprints. Acetone has a higher volatility than water too.

We can find the chromophores for each sample from the UV-Vis analysis by looking at the wavelength. For samples C, D and I, they are having double bond in the structures. While the others, samples A, J and K does not have double bonds. In FTIR analysis, we can examine the stretching and bonding of the compounds from the wavelength that were recorded too.

For sample A, the infrared spectrum of the compound shows that the major absorptions are found at 3319.21 cm-1 and 2973.13 cm-1. These correspond to the OH and CH stretch. From this, we have expected that compound A is ethanol, CH3CH2OH. As compound A do not has double bonds, thus it was not detected by the instrument. The peak obtained was 213.25 nm and compound A undergoes an n* transition at max = 180 nm. This was proven below. The reaction given in the information is :

We know that compound B is ethanal, CH3CHO from the infrared spectrum of 1730 cm-1 and undergoes an n* transition with max = 289 nm. The reagent, Pyridinium chlorochromate (PCC) and dichloromethane, CH2Cl2 is a reaction of oxidation as below,

Equation 1 Oxidation of Alcohol

For sample C, the infrared spectrum of the compound shows that the major absorptions are found at 3039.82 cm-1 and 1704.49cm-1. These correspond to the OH and C=O stretch. From this, we have expected that compound C is ethanoic acid, CH3COOH. The peak obtained was 214.09 nm and compound C undergoes an n* transition. From equation 1, we can see that oxidation of aldehyde can form a carboxylic acids. That means that compound B, CH3CHO form compound C, CH3COOH.

For sample D, the infrared spectrum of the compound shows that the major absorptions are found at 1736.53cm-1 and 1233.50 cm-1. These correspond to the C=O and C-O stretch. From this, we have expected that compound D is ethyl ethanoate, CH3COOHCH2CH3. The peak obtained was 214.13 nm and compound D undergoes an np* transition. This was proven below.The second reaction given in the information is as follows,

From the above reaction, we know that ethanol reacts with ethanoic acid to produce compound D. In the presence of concentrated hydrochloric acid, HCl as a catalyst, reaction between alcohol and carboxylic acid will produce an ester (Clark, 2002). In this case, compound D will be CH3COOHCH2CH3.

Next, we have been given the following reaction :

We know that compound G is benzene, C6H5 form the infrared spectrum of 3037 and 1480 cm-1 and undergoes an pp* transitions with max = 178 nm. From the reaction 3 above, we can decide what is compound represented by H. From the reaction of Friedel-Crafts alkylation with chloromethane, CH3OH in the presence of iron (III) chloride, FeCl3 as catalyst, benzene will turn to toluene, C6H4CH3 which is compound H. Compound H form infrared spectrum of 3033, 1501, and 730 cm-1 and undergo pp* transitions with the max = 260 nm.

For sample I, the infrared spectrum of the compound shows that the major absorptions are found at 2988.99, 1983.75 and 1682.51 cm-1. These correspond to the OH and aromatic C-H and C=O stretch. From this, we have expected that compound I is benzoic acid, C6H5COOH. The peak obtained was 215.11 nm and compound I undergoes * and n* transitions. From reaction 3, we can see that compound I is produced from the oxidation reaction between compound H and the potassium permanganate, KMnO4. We know that KMnO4 oxidizes the methyl group in toluene to form an aromatic carboxylic acid. Therefore, our expectation that compound I is C6H5COOH was true.

For the last reaction is the reaction where sodium hydride in the reaction is a strong base that always be used in a nucleophilic substitution reaction between alcohols with an alkyl halide to produce ether. The reaction above provides the hint to determine compound J and K. We already know that A is ethanol. So, compound J should be the alkyl halide and compound K should be the ether. Only one alkyl halide is available in the list of possible compounds. Thus, compound J is bromoethane or also known as ethyl bromide. Compound J forms the infrared spectrum of 559.05 and 2978.81 cm-1 which represent C-Br and C-H stretch respectively. The peak obtained was 215.11 nm. Ethyl bromide does not have any double bond.

From reaction 4, we can recognize that, compound K is an ether. The infrared spectrum of the compound shows that the major absorptions are found at 1118.25 cm-1. This corresponds to the C-O-C stretch. Thus, compound K is diethyl ether, (C2H5)2O. The peak obtained was 213.37 nm and compound K undergoes n* transition at max = 180 nm which beyond the UV-visible region.

CONCLUSION

This experiment was carried out in order to identify 6 unknown organic compounds via the FTIR and UV-Vis analysis. Based from the experiment, compound A is an alcohol (ethanol), compound C is a carboxylic acid (ethanoic acid), compound D is an ester (ethyl ethanoate), compound I is an aromatic carboxylic acid (benzoic acid), compound J is an alkyl halide (ethyl bromide), and compound K is an ether (diethyl ether). The data was analysed based on the peaks appeared both on the IR and the UV-Vis spectra. The presence or absence of functional groups in all of the compounds could be detected by using the IR spectroscopy. The functional group can be known by analysed the peaks of the spectra. While the UV-Vis spectroscopy only analysed the compounds that contain at least one double bond. The results are in good agreement with the information found in the literature. However, there might be a few differences from the experiment. There might be impurities in some of the samples which finally affected the resulting peaks. This could be caused by handling the laboratory equipment and procedures carelessly and other reasons referred to in the discussions section. In IR spectroscopy, the obtained spectra are resulted from the absorption of light when the radiant energy matches the energy of a specific molecular vibration. While the UV-Vis spectra correspond to the absorption that occurs during the transition of an electron from the ground state to one of the many vibrational and rotational energy states. Besides the minor error in the results, this experiment has been a success since the aim of the experiment was achieved and we gained knowledge regarding the IR and UV-Vis spectroscopy. RECOMMENDATIONSThere are several recommendations that can be deduced from this experiment to improve the results of this experiment. While handling the volatile compounds, it is recommended to dilute it with the solvent in a sample bottle with stoppered to avoid the sample from being vaporized.

The amount of compound being diluted can also be the argument. It is possibly inaccurate using the dropper to transfer a sample portion into the sample bottle. Therefore, we can use automatic or digital pipette that can increase the reliability in the accuracy of the sample amount.

When conducting the UV-Vis analysis, the cuvettes should be handling with care. The cuvette should be held on the rough sides in order to make sure there is no fingerprint on the smooth sides that would probably affect the resulting peak. The outer of the cuvettes also must be wiped gently with tissue so that the traces of spills can be eliminated and to avoid any scratch on the smooth sides.

While conducting the IR analysis, the sample plate should be cleaned with acetone. The plate should be wiped gently with tissue in order to prevent the instantaneous damage because the plate is very sensitive. Dropping the samples onto the plate must be done immediately because if dropping too slowly the volatile sample will vaporize and the result will not be accurate.

In this experiment, we have 6 unknown organic compounds. Since all the compounds are colourless, it is necessary to label the sample bottles to avoid the mismatch information of the compound with the obtained results.

REFERENCES1. Andrew R Barron, 2010, Basic of UV-Visible Spectroscopy http://cnx.org/content/m34525/latest/2. D. A. Skoog, F. J. Holler, S. R. Crouch,Principles of Instrumental Analysis, 6thEd., Thomson Brooks/Cole (2007).

3. Clark, J., 2002. The Mechanism for the Esterification Reaction http://www.chemguide.co.uk/physical/catalysis/esterify.html4. Bruice, P. Y., 2002. Chapter 13 : Mass Spectrometry and Infrared Spectroscopy. In: Organic Chemistry. 4 ed. USA: Prentice-Hall, Inc., pp. 482-525.5. Doudlas A.Skoog, F.James Holler,Stanly R.Crouch,Principles of Instrumental Analysis Sixth Editon,2007, Chapter 16(430-443)6. FTIR Instrumentation. Adopted from the FTIR lab instruction by H.-N. Hsieh, New Jersey Institute of Technology http://www-ec.njit.edu/~hsieh/ene669/FTIR.html7. FTIR Instrumentation. Adopted from the FTIR lab instruction by H.-N. Hsieh, New Jersey Institute of Technology http://www.chemguide.co.uk/physical/catalysis/esterify.htmlReaction SEQ Reaction \* ARABIC 1

A PCC B CrO3 C

CH2Cl2 H2SO4

A + C HCl D

Reaction SEQ Reaction \* ARABIC 2

G CH3Cl H KMnO4 I

FeCl3 H2O


A + J NaH K

THF


Oldenburg, A. L ,Eden, J. G.,(2002), Ultraviolet spectroscopy and UV laser,371-477

John C. Gilbert, Stephen F. Martin.,(2002), Experimental organic chemistry : A miniscale and microscale approach QUOTE Edition,Brooks/Cole Thomson Learning.

Anon,(2013). http://www.perkinelmer.com. Retrieve on 3 April 2013.

Mills and George, D.,(2012), Ultraviolet/visible spectroscopy. http://www.astm.org. Retrieve on 16 March 2013.

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Full Report Uv-Vis and Ftir

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