Review of Vapor Phase U.V. Spectra of O-Amino Anisole
 
Dr. Sevak Kumar*
Assistant Professor, Deptt. of Physics, M.B. P.G. College, Dadri, Gautam Budh Nagar, U.P. India
E-mail: sevaknagar@gmail.com
Abstract - The vapour phase U.V. spectra of O-Amino Anisole in the region 400–200 nm have been studied. The spectra have been analyzed for said molecule. . (i) The assignment of observed frequencies to the probable modes and correlation with other molecules. (ii) The assignment of modes of functional group i.e. –OCH3 , amino group vibrational analysis in the above said molecule with correlation to the assignments of similar n–heterocyclic compounds. The complete interpretation of wave no., bands, transitions (such as π–π* & η–π* bands) with different shifts, 0, 0 bands, ground and excited state fundamentals of vapour state have been discussed and depicted.
Keywords: Vapour phase, UV spectra, π–π* & n –π* transitions.
1. INTRODUCTION
The complete interpretation of spectroscopic studies [1–12] and at length survey [13–23] pointed out that benzene & its derivatives, n–heterocyclic compounds with its derivatives, methoxy benzene and its derivatives are of considerable importance due to biological, ecological & mSedicinal aspects. Methoxy benzene is more electron rich than C6H6 because of the resonance effect of the methoxy group upon the aromatic ring. The resonance effect has greater effect upon the π cloud of ring than the inductive effect. It reacts with electrophiles in the electrophilic aromatic substitution reaction rapidly than C6H6 which in turn reacts rapidly than nitrobenzene [9, 11]. Derivatives of methoxy benzenes occures naturally in a variety of foods and plants such as fennel [9]. C. Miller et al. [10]. N.R. Drink water [12] have shown the chronic toxicity, carcinogenicity, genotoxicity over rats of allyl methoxy benzene.
B.M. Reddy et. al. [13] G.N.R. Tripathi, [14] have studied a broad range of activities (spectroscopic, chemical & biological) over substituted methoxy benzenes. N.M. Griffiths [15] has shown the sensory properties of the chloronated methoxy benzenes.
Not only this H.G. Bray et.al. [16, 17] have shown the metabolic activity of methoxy benzene derivatives in Rabbit which proves the biological importance of these compounds with the support of W.V. Thorpe et.al. [17] Satyaprakash [18] has shown the important study on fluorescence spectrum of vapour methoxy benzene K.V.V. Krishna Mohan [19] has presented the dielectric investigations & novel bromination method for methoxy benzene derivatives. Which may be useful for manufacture of fine chemicals, antiviral & antibacterial drugs, Methoxy benzenes are the derivatives made by substituted anisoles and related to each other, so it is worthwhile to study comperativly with substituted anisoles.
The study of bioactive compounds such as pyridine, pyrimidine, cytosine, methoxy benzene, anisoles, furan, uracil and its derivatives are showing significance in spectroscopic and pharmaceutical field. Methoxy Benzenes have great biological importance in heterocyclic chemistry [24-27]
The electronic spectra and azabenzenes states had been significantly studied both experimentally & theoretically. The η–π* transition in said molecules and mostly diffuse but these η–π* transitions where the electron’s promotion from a nonbonding orbital localized on the nitrogen atom to an antibonding π* orbital, give rise to sharp spectra at longer wavelengths. Theory predicts [35–38, 48] at least two such transitions, one symmetry allowed and one forbidden. Even though experimentally and theoretically are in good agreement as far as the π*–π states are concerned, same is not true for π*–η states. Absorption spectra of cytosine nucleosides and uracil have been well predicted theoretically by Berthod et.al. [28], Clark & Tinocoo [29] had found evidence of electronic transitions present other than η–π* and π*–π in the spectra of cytosine, uracil and their nucleosides.
S.P. Gupta et.al. [30] had studied the U.V. spectra of 2, 3-dichloro, 2, 6–dichloro & 2–amino–4–chloro anisole and found the π*–π transitions in vapor phase at 35248, 35868 & 33389 cm–1, in methanol at 35174, 35987 & 33670 cm–1, in chloroform 35081, 35855, 33501 cm–1, in benzene at 35001, 35816, 33367 cm–1. in carbon tetrachloride at 35952, 35739 & 33225 cm–1 for substituted anisole respectively followed by R.K. Goel et.al. [31, 32] C. Passingham [37] had studied and interpreted the nitro functional group frequencies and bands of various nitro compounds such as nitrobenzene, 1, 3–dinitrobenzene, 1, 3, 5–Dinitrobenzene, 1, 2–dinitrobenzene etc. and also done by Baraka [38].
So in consideration to the above this work has under taken for the compound named o-Amino Anisole to study with the aim the U.V. spectra in the region 400–200 NM in vapor state. (i) The assignments of observed frequencies to the probable modes and correlation with other molecules. (ii) The assignment of modes of functional group i.e. –OCH3, amino present in the above said molecule with correlation to the assignments of similar n–heterocyclic compounds. The complete interpretation of wave no., bands, transitions (such as π–π* & η–π* bands) with different shifts, 0, 0 bands, ground and excited state fundamentals of vapour state U.V. spectrum of said molecule.
2. MATERIAL–METHOD:
The spec-pure chemicals Benzene, o-Amino Anisole (here after referred as o–AA) were obtained from the m/s- Sigma-Aldrich chem.co. USA & used as such without further purification. However, their purity was confirmed by elemental analysis & M.P. determination. A few mg of the polycrystalline sample was mixed with spec grade KBr and passed in to disc. The spectral width was 0·2 cm–1 and the scanning speed was 30 cm–1 per minute. Frequencies of all sharp bands are accurate to + cm–1.
3. RESULT OF ANALYSIS
The observed bands position & their complete analysis in Vapour Phase near u.v. absorption spectra of & correlation of 0-0 bands of O-AA with othersimiler molecules are shown in Table 1 &2 with assignments of the fundamentals to the probable modes of vibration (ground & excited state). While the vapour phase U.V. spectra is shown in Fig. 2.
S.N. Sharma [4] has well studied the vapour phase U.V. spectra of substituted anisoles. Also Marjit et.al. [8] Have studied the U.V. spectra of substituted methyl anisoles. Gupta et al.[42] have also been well described the U.V. spectra and solvent effect on π–π* transition in chloro substituted anisoles. The correlation of π–π* and η–π* electronic transitions of present molecule with similar molecules are depicted in Table 4.As seen from the ultra-violet spectrum of benzene [33–35], the B-band at 254 mm shows a great deal of fine structure in the vapour state. In hexane solution benzene shows absorptions at 184 mm, emax 60,000, 204mm, emax 7400 and 254 mm, emax 204. The band at 254 mm is the result of forbidden transitions in highly symmetrical benzene molecule. Benzene shows a series of low intensity bands between 230 & 270, mm The u.v. spectrum of heterocyclic aromatic compounds can be compared with Cyclopentadiene.
In these compounds, a forbidden band (R-band) due toπ–π* transition is also observed with very low value of emax. In furan, a band at 252 mm, emax 1, in addition to an intense band at 200 mm, emax 10,000. The chromophoric or auxochromic substitution brings about bathochromic as well as hyperchromic shift [34–40].
The observed vapour phase u.v. spectra as shown in Fig. 4, clearly shows two band systems lying in the region 2800 to 2100 A°. [49, 50]. The system close to the higher wave length has been correlated to n–π* system & that close to the lower wave length (which is very strong as expected) to the π–π* system of Benzene, several workers have reported this nature lead to red shift. [34, 35, 45]. In conformity, the allowed nature of the transition & nature of the observed absorption spectrum in vapour-phase recorded at different wave lengths of the absorbing path & different temp., the molecule O-AA shows two distinct fairly intense systems [n–π* &π–π* systems] of bands. In accordance with the similar assignments in case of substituted benzenes [4, 7, 43–46], the observed band system having very intense band at 42016 cm–1 has been designated to n–π* transitions and at 34482 cm–1 named to π–π* system, which are analogous to 2100 A°& 2600 A° system of benzene. This system of bands corresponds to the system of bands observed in the same region [20–23, 30–40].
The n–π* system which correspond to B1 – A1, [π*–n] transition has been analyzed in terms of ground state, excited state fundamentals and their combinations. In this system the bands at 1368,1195,1050,840,570,470,430,380,343,280,187,108,54,70,180,230,323,350,370,456,590,890,1010,1230,1385 cm–1 have been assigned to E.S. & G.S. fundamentals with 0, 0 band at 42016 cm–1. These bands show good correlation with the I.R. & Raman spectral frequencies supported by several workers [16, 17, 20–23].
On the other hand, the system of band with vibronic structures is observed and it has been identified as the π–π* transition system. In these bands the highly intense band at 35880 cm–1 has been identified as 0, 0 band, which is in accordance with the system observed in the same region [4, 7,35]. In this system the bands having the spacing 674,300,190,80,50,30-, 70,120,240,260,335,405,950,1300 are attributed to ground state & excited state fundamentals. These bands are in good agreement to the work given by several workers such as Goel et al. [43], Srivastava et al. [41], and others [4, 7]. The observed bands show good relationship with the values at 36640 & 4700 cm–1 for π–π* & η–π* system given by Srivastava et al. [41]. The interpretation cited above is in accordance with the work [4, 7, 51,44–46].
These are in agreement with similar E.S. fundamentals obtained by Sharma [4] at 208, 380, 685, 795, 1264 cm–1 in m-and p-methyl anisole and by Marjit & Banerjee [8] at 342, 532, 601, 775, 830, 971, 1012, 1270, 1415, 1570 cm–1 in m-Bromo anisole similarly the bands towards higher wavelength side have been taken as the fundamentals of the ground state.
Gupta et.al.[42] have found the 0, 0 bands at 35248 cm–1 and at 35868 cm–1 in case of 2, 3 and 2, 6-dichloro anisole and the G.S. & E.S. absorption and at 271, 550, 990, 1350, 1657/339, 594, 814, 1449, 1584 cm–1 and at 293, 619, 927, 1703/246, 668, 897, 1169, 1348, 3043 cm–1 in both molecules. All these results show the good relationship with the study of present work of said molecules.
Figure 1: Molecular Structure of o-AA
Figure 2: Vapour Phase U.V of O-AA
Table 1: Correlation of n-π* & π−π* transitions of O- AA with similar molecules (all values in cm-1)
Sl No.
Molecules
n−π*
Transition
π−π*
Transition
1.
2, 3-Dichloroanisole +
—
35248
2.
2, 6- Dichloro anisole +
—
35868
3.
2-Amino-4-Chloro anisole+
—
33389
4.
Anisole+
47619
38461
5.
2-Amino-4-methyl pyrimidine +
43937
36101
6.
5-Ethyl-2- methyl pyrimidine +
47600
36640
7.
2-Hydroxy-5-Nitro pyridine+
48543
33333
8.
O - AA*
42016
34482
 
+. Ref –7, * - Present work
 
Table 2: Analysis of the Electronic Absorption Bands With 0,0 Band & Ground, Excited State Modes for o – AA All values in cm-1
Position of Bands With intensity
Separation from 0,0 bands (cm-1)
ASSIGNMENTS
n−π* system
40648
0–1368
0–1368
40821
0–1195
0–1195
40966
0–1050
0–1050
41176
0–840
0–840
41446
0–570
0–570
41546
0–470
0–470
41586
0–430
0–430
41636
0–380
0–380
41673
0–343
0–343
41736
0–280
0–28
41889
0–187
0–187
41908
0–10 8
0–10 8
41962
0–54
0–54
42016 vvs
0, 0 band
0–0, 0 band
42086
0+70
0+70
42196
0+180
0+180
42246
0+230
0+230
42339
0+323
0+323
42366
0+350
0+350
42386
0+370
0+370
42472
0+456
0+456
42606
0+590
0+590
42906
0+890
0+890
43026
0+1010
0+1010
43246
0+1230
0+1230
43401
0+1385
0+1385
π-π * system
33808
0–674
0–674
34182
0–300
0–300
34292
0–190
0–190
34402
0–80
0–80
34432
0–50
0–50
34452
0–30
0–30
34482
0, 0 band
0, 0 band
34552
0+70
0+70
34602
0+120
0+120
34722
0+240
240
34742
0+260
0+884
34817
0+335
0+335
34887
0+405
0+405
35432
0+950
0+950
32782
0+1300
0+1300
 
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