Functional Group Identifier / Organic Groups & Reactions

Look up alcohol, aldehyde, ketone, acid, ester, amine, amide and ether groups: formula, polarity, common reactions and uses, with identification tips.

Quick 1-Click Functional Group Archetypes

Functional Class Selection & Compound Specifier

Reactivity Index
7/ 10
Electrophile / Nucleophile affinity
Dipole Polarity
8/ 10
Hydrogen bonding & water solubility
Relative Acidity
5/ 10
Approximate pKa: 15 - 18
Relative Basicity
2/ 10
Lewis base electron donation

Property Profile Comparison: Alcohol vs Carboxylic Acid

Relative educational scaling from 1 (lowest) to 10 (highest).

Signature Reactions for Alcohol

OxidationReagent: PCC or K₂Cr₂O₇ / H₂SO₄
Primary Alcohol + [O]Aldehyde / Carboxylic Acid
EsterificationReagent: H₂SO₄ catalyst, reflux
Alcohol + Carboxylic AcidEster + Water
DehydrationReagent: Conc. H₂SO₄ (170°C)
Alcohol + HeatAlkene + Water
IR Fingerprint:3200 - 3600 cm⁻¹ (broad O-H stretch)

Organic Functional Groups Master Cheat Sheet (8 Common Classes)

Systematic overview of chemical formulas, IUPAC naming affixes, IR diagnostic peaks, and representative molecules.

ClassGeneral FormulaIUPAC AffixIR Absorption (cm⁻¹)Approx pKaSample Molecule
AlcoholR-OHhydroxy- / -ol3200 - 3600 cm⁻¹ (broad O-H stretch)15 - 18CH₃CH₂OH
AldehydeR-CHOformyl- / oxo- / -al1720 - 1740 cm⁻¹ (C=O) & 2720, 2820 cm⁻¹ (Fermi doublet C-H)16 - 20 (α-hydrogen)CH₃CHO
KetoneR-CO-R'oxo- / -one1705 - 1725 cm⁻¹ (sharp C=O stretch)19 - 21 (α-hydrogen)CH₃COCH₃
Carboxylic AcidR-COOHcarboxy- / -oic acid2500 - 3300 cm⁻¹ (very broad O-H) & 1710 cm⁻¹ (C=O)4 - 5CH₃COOH
EsterR-COO-R'alkoxycarbonyl- / -oate1735 - 1750 cm⁻¹ (C=O) & 1050 - 1300 cm⁻¹ (C-O)25 (α-hydrogen)CH₃COOCH₂CH₃
AmineR-NH₂amino- / -amine3300 - 3500 cm⁻¹ (N-H stretch, 1 or 2 spikes)35 - 38 (conjugate acid pKa 9 - 11)CH₃NH₂
AmideR-CO-NH₂amido- / carbamoyl- / -amide1650 - 1690 cm⁻¹ (Amide I, C=O) & 1550 - 1640 cm⁻¹ (Amide II)15 - 17CH₃CONH₂
EtherR-O-R'alkoxy- / -ether1050 - 1150 cm⁻¹ (strong C-O single bond stretch)> 40CH₃CH₂OCH₂CH₃

Worked Identification & Comparison: Alcohol vs Carboxylic Acid vs Amine

Distinguishing structural features, IR diagnostic frequencies, and acid-base behaviors:

Group 1: Hydroxyl (Alcohol)
Ethanol (CH₃CH₂OH) - Neutral pKa ≈ 16
Group 2: Carboxyl (Acid)
Acetic Acid (CH₃COOH) - Acidic pKa ≈ 4.76
Group 3: Amino (Amine)
Methylamine (CH₃NH₂) - Basic conjugate pKa ≈ 10.6
Diagnostic Comparison Steps:
•1. Structural Distinction: Alcohol contains -OH bonded to sp³ carbon; Carboxylic acid has -OH bonded directly to a carbonyl carbon (C=O); Amine has a nitrogen atom with a lone pair.
•2. Infrared (IR) Spectroscopy Diagnostic: Alcohol exhibits broad paraboloid O-H absorption at 3200-3600 cm⁻¹; Carboxylic acid displays massive broad 'beard' from 2500-3300 cm⁻¹ plus sharp C=O at 1710 cm⁻¹; Amine displays 1 or 2 sharp spikes at 3300-3500 cm⁻¹.
•3. Relative Acidity Comparison: Carboxylic acid (score 9/10, pKa ~ 4.8) >> Alcohol (score 5/10, pKa ~ 16) >> Amine (score 1/10, pKa ~ 38). Resonance stabilization of the carboxylate anion accounts for the 10¹¹ acidity difference.
•4. Reaction Coupling: Combining an alcohol with a carboxylic acid under acid catalysis (Fischer esterification) yields an ester with fruit fragrance + water.

💡 Organic Chemist Insight: Functional groups govern the entirety of organic reactivity. Identifying the presence of carbonyl (C=O), hydroxyl (O-H), or amino (N-H) bonds immediately forecasts solubility, IR fingerprint, and synthesis pathways.

Frequently Asked Questions

Quick Tips

  • 1Use consistent units throughout calculations
  • 2Consider significant figures in results
  • 3Document experimental conditions
  • 4Verify results with control calculations