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Gii PhIR - NMR

Ph hng ngoi (FT-IR) v ph cng hng t ht nhn (1H-NMR, 13C-NMR) c coi l 2 cngc c bn nht thc hin php xc nh cu trc cc hp cht hu c.

Cc bc thc hin vic gii 1 bi tp v ph vi cng thc tng qut cho trc.

BC 1. Tnh KHNG BO HAdegree of unsaturation - DU) t trong cng thc tng qut xem trong phn t c bao nhiu vng,

bao nhiu lin kt i.

CnHmOiNl

DU =2

22 mln

VD: C5H10O => DU= 5-10/2+1=1

C8H11N => DU=8-10/2+1 = 4

NU:

(DU= 1 c th c 1 lin kt i hoc vng

DU= 2 c th c 2 lin kt i, 2 vng, 1 lin kt ba hoc 1 lin kt i + 1 vng

DU h li k i li k i li k i li k b

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DU 3 h 3 li k i 3 1 li k i 2 2 li k i 1 1 li k b

BC 4. Kim tra sO, C, H, Hal,...Kim tra ha tr cc nguyn t xem ph hp chaNu cha ng, vit cu trc phn t khc v

kim tra li ti vng s sng ln hn 1500cm-1 xc nh cc lin kt trong phn txem phhp vi cng thc tng qut cha.

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Tn sdao ng c trng ca phIR

1. Carbon-Hydrogen Stretching

sp3 C-H, just below 3000 cm-1 (to the right)

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sp C-H, at 3300 cm-1

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2. O-H and N-H Stretching

u c hp thti ~3300cm-1 nhng hnh dng phli rt khc nhau: O-H peak rng v t cn N-H th

peak rng nhng nhn

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absorbs strongly just above 2200 cm-1. The alkyne signal is much weaker and is just

below 2200 cm-1.

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37002500 cm-1 Single bonds to hydrogen1. Single Bonds to Hydrogen

1900 1500 cm-1 Double bonds

2. Double Bonds

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1400 650 cm-1 Single bonds (other than hydrogen)

4. Single Bonds (not to Hydrogen

5. Bending Vibrations

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