FTIR -- InfraRed

IR1. Bet vis & microwave2. Organic chemists use 4000 - 400 cm-1

3. cm-1 E of vibration

No 2 cmpds give exact sample IR (enantimoers)

2 types of molecular vibration stretching bending

3 vibrations

symmetrical asymmetrical scissoring

Stretching Frequencies ()C-C C-O C-N 1300 - 1500 cm-1

C=C C=O C=N N=O 1900 - 1500C C C N 2300 - 2000C-H O-H N-H 3800 - 2700

2 imprt areas for prelim exam of spectra 4000 - 1300 900 - 650 1300 - 900 fct group region fingerprint complex

Imprt for -OH NH C=Ostrong bands 1600 - 1310 aromatics (benzene ring) 900 - 650 strong out-of-plane bending & ring bending

C - H Stretch

Alkanes 3000 - 2840(s)

other: near 1375 & 1450Cycloalkanes 3100 - 2990(m)

other: near 1450(m)

Alkenes above 3000(s)

other: near 1416(m); 1000-650(w); near 850(s)

Alkynes 3333 - 3267(n,s) stronger-narrower than OH & NH other: 700-610(b,s); 1370-1220(w,o)

Aromatics 3100 - 3000 & 2000 - 1650(w,o)

other: 900-675(s); 1300-1000(m)

Aldehydes 2830 - 2695(2:s) w/ near 1390 other: near 2720(m)

C to C

Alkanes below 500; 1200 - 800(w) are of little value best is C-H CH3 2962 & 2872 CH2 near 2926 & near 2853 (+/-10) CH near 1375 & near 1450

Alkenes 1667 - 1640(m)

Alkynes 2260 - 2100(w)

ALCOHOLS -- PHENOLS

Alkenes - Phenols -OH & C-O OH 3650 - 3584(b,s); 1420 - 1330(m)

CO 1260 - 1000(s)

ETHERSEthers C-O-C similar to C-C-C but more intense 1150 - 1085(s)

CARBONYL C=O containing

Carbonyls (ketones, aldehydes, carboxylic acids, esters, anhydrides, amides) C=O 1870 - 1540(s)

Ketones 1300 - 1100(m)

Aldehydes 1740 - 1720 C-H 2830-2695(2:m) & near 2720(m)

Carboxylic Acids O-H 3300 - 2500(b,s)

C=O near 1766(s)

C-O & O-H near 1320-1210(m) & near 1440-1395(m)

Esters C=O 1750 - 1715(s) higher freq than ketones C-O 1210- 1163(2:s)

NITROGEN CONTAINING

Amides NH2 or NH 1650 - 1515 other: near 3520(m) & near 3400(m)

C=O 1694 & 1650(s)

C-N near 1400(m)

Amine N-H near 3500(w) & near 3400(w)

other: NH 1650-1580(m)

C-N 1250 - 1020(m)

aromatic C-N 1342-1266(s)

Nitriles C=N 2260 - 2222(m)