Shweta thakur Asked a Question
October 2, 2021 10:41 pmpts 30 pts
purities but the ectrum, on the whole, will have itrasSt rast, the spectrum of an 1ptton LiOn bands. On bands. SOME SOLVED PROBLE IS ONIN INFRARED SPECTROSCOPY XAmple 1. How will you differentiate between the following pairs of compounds by IR speciroscopy () CHCHO and CH,COCH, (G) CH,CoCH,CH, and CH,COCH- CH, (in) CH CH OH and CH,OCH, (iv) 3-pentanone and cyclopentanone (v) CH,COCl and CICH,COOH. Solution. () Both benzaldehyde and acetophenone contain a carbonyl group and would thus show a Strong C=Ostretch at 1700 and 1680 cmrespectively, But the most important difference is that benzaldehyde Shows two weak absorption bands in the region 2860-2820 and2760-2720 due to CH stretching o he - HO group. These peaks are, however, absent in the spectrum of acetophenone. (i) CH, COCH,CH is a saturated ketone and would absorb around 1715 cm In contrast, CH,COCH= CH, is an o, B-unsaturated ketone. Therefore, it will absorb around 1680-1690 cm about 20-30 cm lower than that of CH,COCH, CH iii) Ethyl alcohol (CHCH,OH) would show a broad strong band in the region 3400-3200 cm due to H- onded O-H stretching vibration alongwith a strong C-0 stretching vibration in the region 150-1100 cm In contrast, dimethyl ether will show only a strong C-0 stretching in the region 50-1000 cm (v) CH,COCH,CH,CH, and 0 are both saturated ketones. Cyclopentanone because of the ring in absorbs at higher frequency i.e. at 1740 cm but CH,COCH,CH,CH, absorbs at its usual position of Scm (The most distinguishing feature of the IR spectra of the two compounds is that CICH, COOH will a strong and broad band in the region 3400-2500 cm due H-bonded O-H stretching vibration while ch absorption will appear in the IR spectrum of CH, COCI rOup but it is separated by a CH, group in ClCH,COOH. As a result, Cl exerts a much stronger-1-effect Ocithan in CCH,COOH Consequently C0stretching vibration will appear at a much higher Another distinguishing feature of the IR spectra of the two compounds is that the C= O stretching Ons of the two compounds will be widely different. In CH, COCI, Cl atom is directly attached to the around 1800 cm in CH, COCl while in CiCH, COOH, C=O stretching vibration is expected to nd 1735 cm
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  • Shreyasi majumdar 1 Best Answer
    kindly go through this book. It will help
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