Organic Chemistry II Functional Groups

General structure: R–O–R'

IUPAC naming: prefix alkoxy-

Example: Dimethyl ether (CH3OCH3)

Reactivity: Generally inert, weakly nucleophilic oxygen

Spectroscopy: IR C–O stretch ~1050-1150 cm^-1, 1H NMR alkyl protons 3.3-4 ppm (near oxygen)

General structure: Three-membered cyclic ether (triangle with O)

IUPAC naming: suffix -irane

Example: Ethylene oxide (C2H4O)

Reactivity: Highly strained, electrophilic ring-opening

Spectroscopy: IR C–O–C stretch ~1250 cm^-1, 1H NMR ring protons 2.5-3.5 ppm

General structure: R–SH

IUPAC naming: suffix -thiol, prefix mercapto-

Example: Ethanethiol (C2H5SH)

Reactivity: Weak acid, nucleophilic sulfur

Spectroscopy: IR S–H stretch ~2550-2700 cm^-1, 1H NMR SH proton ~1-3 ppm

General structure: R–S–R'

IUPAC naming: prefix alkylthio-

Example: Dimethyl sulfide (CH3SCH3)

Reactivity: Nucleophilic sulfur, less reactive than thiol

Spectroscopy: IR C–S stretch ~700 cm^-1, 1H NMR alkyl protons 2-3 ppm (near S)

General structure: RNH2 (1°), R2NH (2°), R3N (3°)

IUPAC naming: suffix -amine, prefix amino-

Example: Methylamine (CH3NH2)

Reactivity: Basic, nucleophilic nitrogen

Spectroscopy: IR N–H stretch ~3300-3500 cm^-1, 1H NMR NH protons 1-5 ppm (broad)

General structure: RCHO

IUPAC naming: suffix -al

Example: Formaldehyde (HCHO)

Reactivity: Electrophilic carbonyl carbon

Spectroscopy: IR C=O stretch ~1720 cm^-1, 1H NMR aldehyde proton 9-10 ppm

General structure: RCOR'

IUPAC naming: suffix -one

Example: Acetone (CH3COCH3)

Reactivity: Electrophilic carbonyl carbon

Spectroscopy: IR C=O stretch ~1715 cm^-1, 1H NMR alpha protons 2-2.5 ppm

General structure: RCOOH

IUPAC naming: suffix -oic acid

Example: Acetic acid (CH3COOH)

Reactivity: Acidic, electrophilic carbonyl

Spectroscopy: Broad IR O–H stretch ~2500-3300 cm^-1, C=O stretch ~1710 cm^-1, 1H NMR acidic proton 10-13 ppm

General structure: RCOCl

IUPAC naming: suffix -oyl chloride

Example: Acetyl chloride (CH3COCl)

Reactivity: Very reactive electrophile, nucleophilic acyl substitution

Spectroscopy: IR C=O stretch ~1800 cm^-1, 1H NMR alpha protons 2-2.5 ppm

General structure: (RCO)2O

IUPAC naming: suffix -oic anhydride

Example: Acetic anhydride ((CH3CO)2O)

Reactivity: Reactive electrophile, nucleophilic acyl substitution

Spectroscopy: IR C=O stretches ~1800 and 1750 cm^-1, 1H NMR alpha protons 2-2.5 ppm

General structure: RCOOR'

IUPAC naming: suffix -oate

Example: Ethyl acetate (CH3COOCH2CH3)

Reactivity: Less reactive electrophile, nucleophilic acyl substitution

Spectroscopy: IR C=O stretch ~1735 cm^-1, 1H NMR alpha protons 2-2.5 ppm

General structure: RCONR'R''

IUPAC naming: suffix -amide

Example: Acetamide (CH3CONH2)

Reactivity: Least reactive electrophile, resonance stabilized

Spectroscopy: IR C=O stretch ~1650 cm^-1, N–H stretch ~3200-3500 cm^-1, 1H NMR NH protons 6-8 ppm

General structure: R–C≡N

IUPAC naming: suffix -nitrile

Example: Acetonitrile (CH3CN)

Reactivity: Electrophilic carbon, polar triple bond

Spectroscopy: IR C≡N stretch ~2200-2250 cm^-1, 1H NMR alpha protons 2-3 ppm

General structure: R2C=NR'

IUPAC naming: suffix -imine

Example: Benzylideneaniline (C6H5CH=NC6H5)

Reactivity: Electrophilic C=N, nucleophilic N

Spectroscopy: IR C=N stretch ~1640-1690 cm^-1, 1H NMR imine proton 7-9 ppm

General structure: Alkene adjacent to amine: R2C=CR–NR2

IUPAC naming: no special suffix, named as substituted amines

Example: N,N-Dimethyl enamine

Reactivity: Nucleophilic alkene, reacts with electrophiles

Spectroscopy: IR C=C stretch ~1600-1650 cm^-1, 1H NMR alkene protons 4.5-6 ppm

General structure: Enol: R–C=C–OH; Enolate: R–C=C–O^-

IUPAC naming: no special suffix, tautomers of carbonyls

Example: Acetaldehyde enol form

Reactivity: Nucleophilic at alpha carbon

Spectroscopy: IR O–H stretch ~3200-3600 cm^-1, 1H NMR vinyl protons 4.5-6 ppm

General structure: R–CH(OH)–OR'

IUPAC naming: intermediate, no suffix

Example: Glucose cyclic hemiacetal

Reactivity: Intermediate in acetal formation

Spectroscopy: IR O–H stretch broad, 1H NMR anomeric proton 4.5-5.5 ppm

General structure: R–CH(OR')2

IUPAC naming: no suffix, protected aldehyde/ketone

Example: Dimethyl acetal of acetaldehyde

Reactivity: Stable protecting group, inert to bases

Spectroscopy: IR no carbonyl stretch, 1H NMR acetal protons 4.5-5.5 ppm

General structure: R–CH=CH–C=O–R'

IUPAC naming: suffix -enone

Example: Mesityl oxide

Reactivity: Conjugate (Michael) addition electrophile

Spectroscopy: IR C=O stretch ~1680-1700 cm^-1, 1H NMR vinyl protons 5.5-7 ppm

General structure: R–NO2

IUPAC naming: prefix nitro-

Example: Nitrobenzene (C6H5NO2)

Reactivity: Electron withdrawing, deactivates aromatic ring

Spectroscopy: IR asymmetric stretch ~1520-1550 cm^-1, symmetric ~1340-1380 cm^-1

General structure: Six-membered ring with one N

IUPAC naming: pyridine

Example: Pyridine (C5H5N)

Reactivity: Basic nitrogen, electrophilic substitution on ring

Spectroscopy: IR ring modes ~1600 cm^-1, 1H NMR aromatic 7-9 ppm

General structure: Five-membered ring with one N

IUPAC naming: pyrrole

Example: Pyrrole (C4H5N)

Reactivity: Electron rich, electrophilic substitution

Spectroscopy: IR N–H stretch ~3400 cm^-1, 1H NMR aromatic 6-7 ppm

General structure: Five-membered ring with one O

IUPAC naming: furan

Example: Furan (C4H4O)

Reactivity: Electron rich, electrophilic substitution

Spectroscopy: IR C–O stretch ~1050-1150 cm^-1, 1H NMR aromatic 6-7 ppm

General structure: Five-membered ring with one S

IUPAC naming: thiophene

Example: Thiophene (C4H4S)

Reactivity: Electron rich, electrophilic substitution

Spectroscopy: IR C–S stretch ~700 cm^-1, 1H NMR aromatic 6.5-7.5 ppm

Most reactive to least reactive: Acid chloride > Acid anhydride > Ester > Amide

Reason: Leaving group ability and resonance stabilization

Acidity (pKa approx): Carboxylic acid (~4-5) > Phenol (~10) > Alcohol (~16) > Terminal alkyne (~25) > Amine (~35)

Aldehyde or ketone carbonyl (C=O stretch)

Aldehyde proton

Alcohol or phenol O–H stretch