Overview
This lecture covers the concept of functional groups in organic chemistry, how to identify them, and important distinctions between similar groups.
Functional Groups and the R Group
- Functional groups are specific atom groupings in organic molecules that determine their chemical reactivity.
- The "R group" represents the rest of the molecule not currently being focused on.
- In structures, R-functional group notation shows that any molecule can contain the group.
Types of Carbon Chains
- Alkanes have only single bonds (no pi bonds), with sp3 hybridized carbons and 109.5° bond angles.
- Alkenes have at least one double bond (pi bond), with sp2 hybridized carbons and 120° bond angles.
- Alkynes have a triple bond, with sp hybridized carbons and 180° bond angles.
- The naming endings: "ane" (single), "ene" (double), "yne" (triple).
Halides and Amines
- Alkyl halide (haloalkane): hydrocarbon with a halogen (F, Cl, Br, I) attached.
- Amines contain nitrogen bound to carbon(s): primary (1 R), secondary (2 R), tertiary (3 R), or quaternary (4 R, positive charge).
Alcohols and Thiols
- Alcohol: R–OH (hydroxyl group) attached to carbon; classified as primary, secondary, or tertiary.
- Thiol: Like alcohol but with sulfur (R–SH) instead of oxygen.
Ethers and Epoxides
- Ether: R–O–R (oxygen between two carbons), can be symmetrical or asymmetrical; cyclic ethers include tetrahydrofuran (THF).
- Epoxide: A three-membered ring with two carbons and one oxygen; highly reactive.
Carbonyl Compounds
- Carbonyl group: C=O present in several functional groups.
- Ketone: Carbonyl in the middle of a chain, flanked by R groups (R–CO–R').
- Aldehyde: Carbonyl at end of chain, adjacent to hydrogen (R–CHO).
Carboxylic Acids and Derivatives
- Carboxylic acid: Carbonyl attached to OH at the end of chain (R–COOH or R–CO2H).
- Ester: Carboxylic acid with OH replaced by OR group (R–CO2R').
- Amide: Carboxylic acid with OH replaced by NH2 or other nitrogen-containing group (R–CONH2).
- Nitrile: Carbon triple-bonded to nitrogen (R–C≡N).
Phenol vs. Phenyl
- Phenol: Benzene ring with an OH group (aromatic alcohol).
- Phenyl: Benzene ring as a substituent on a larger molecule (aromatic ring attached to R).
Key Terms & Definitions
- Functional Group — specific atom grouping in an organic molecule that determines its reactivity.
- R Group — the unspecified "rest of the molecule" in a structure.
- Alkane — molecule with only single C–C bonds.
- Alkene — molecule with at least one C=C double bond.
- Alkyne — molecule with a C≡C triple bond.
- Alkyl Halide — carbon chain with a halogen attached.
- Amine — molecule with nitrogen bound to carbon(s).
- Alcohol — R–OH functional group.
- Thiol — R–SH functional group.
- Ether — R–O–R functional group.
- Epoxide — three-membered ether ring.
- Carbonyl — C=O group.
- Ketone — carbonyl flanked by carbons (R–CO–R').
- Aldehyde — terminal carbonyl (R–CHO).
- Carboxylic Acid — R–COOH, carbonyl with OH.
- Ester — R–CO2R', carboxylic acid derivative.
- Amide — R–CONH2, carboxylic acid with NH2.
- Nitrile — R–C≡N group.
- Phenol — benzene ring with OH.
- Phenyl — benzene ring as a substituent.
Action Items / Next Steps
- Download the functional group cheat sheet from the provided website.
- Try the practice quiz on functional groups.
- Begin the naming series for functional groups (IUPAC and common names).