Examples of Common Functional Groups

Classification and Examples of Common Functional Groups

  • Definition of General Notation:

    • In organic chemical structural formulas, the variable designation RR refers to the remainder of the organic compound, which typically consists of carbon and hydrogen atoms.

  • Alkyl Halide:

    • General Structure: R−X¨:R-\ddot{X}:
    • Halogen Identity: X=Cl, Br, or IX = \text{Cl, Br, or I}
    • Classification: Alkyl halide
    • Example Compound: n-Propyl chloride (CH3CH2CH2ClCH_3CH_2CH_2Cl)
    • Textbook Reference: Chapter 7

  • Alkene:

    • General Structure: R2C=CR2R_2C=CR_2 (characterized by a carbon-carbon double bond)
    • Classification: Alkene
    • Example Compound: 1-Butene (CH2=CHCH2CH3CH_2=CHCH_2CH_3)
    • Textbook Reference: Chapters 7, 8

  • Alkyne:

    • General Structure: R−C≡C−RR-C\equiv C-R (characterized by a carbon-carbon triple bond)
    • Classification: Alkyne
    • Example Compound: 1-Butyne (HC≡CCH2CH3HC\equiv CCH_2CH_3)
    • Textbook Reference: Chapter 9

  • Alcohol:

    • General Structure: R−O¨HR-\ddot{O}H
    • Classification: Alcohol
    • Example Compound: 1-Butanol (CH3CH2CH2CH2OHCH_3CH_2CH_2CH_2OH)
    • Textbook Reference: Chapter 12

  • Ether:

    • General Structure: R−O¨−RR-\ddot{O}-R
    • Classification: Ether
    • Example Compound: Diethyl ether (CH3CH2OCH2CH3CH_3CH_2OCH_2CH_3)
    • Textbook Reference: Chapter 13

  • Thiol:

    • General Structure: R−S¨HR-\ddot{S}H
    • Classification: Thiol
    • Example Compound: 1-Butanethiol (CH3CH2CH2CH2SHCH_3CH_2CH_2CH_2SH)
    • Textbook Reference: Chapter 13

  • Sulfide:

    • General Structure: R−S¨−RR-\ddot{S}-R
    • Classification: Sulfide
    • Example Compound: Diethyl sulfide (CH3CH2SCH2CH3CH_3CH_2SCH_2CH_3)
    • Textbook Reference: Chapter 13

  • Aromatic (or Arene):

    • General Structure: Hexagonal aromatic benzene ring with alternating single and double bonds or delocalized π\pi electron cloud attached to an RR group
    • Classification: Aromatic (or arene)
    • Example Compound: Methylbenzene (C6H5CH3C_6H_5CH_3)
    • Textbook Reference: Chapters 17, 18

  • Ketone:

    • General Structure: R−C(=O)−RR-C(=O)-R (carbonyl group bonded to two carbon-containing RR groups)
    • Classification: Ketone
    • Example Compound: 2-Butanone (CH3COCH2CH3CH_3COCH_2CH_3)
    • Textbook Reference: Chapter 19

  • Aldehyde:

    • General Structure: R−C(=O)−HR-C(=O)-H (carbonyl group bonded to an RR group and a hydrogen atom)
    • Classification: Aldehyde
    • Example Compound: Butanal (CH3CH2CH2CHOCH_3CH_2CH_2CHO)
    • Textbook Reference: Chapter 19

  • Carboxylic Acid:

    • General Structure: R−C(=O)−OHR-C(=O)-OH (carbonyl group bonded to a hydroxyl group)
    • Classification: Carboxylic acid
    • Example Compound: Pentanoic acid (CH3CH2CH2CH2COOHCH_3CH_2CH_2CH_2COOH)
    • Textbook Reference: Chapter 20

  • Acyl Halide:

    • General Structure: R−C(=O)−XR-C(=O)-X (carbonyl group bonded to a halogen X=Cl, Br, or IX = \text{Cl, Br, or I})
    • Classification: Acyl halide
    • Example Compound: Acetyl chloride (CH3COClCH_3COCl)
    • Textbook Reference: Chapter 20

  • Anhydride:

    • General Structure: R−C(=O)−O−C(=O)−RR-C(=O)-O-C(=O)-R (two acyl groups linked by a central oxygen atom)
    • Classification: Anhydride
    • Example Compound: Acetic anhydride ((CH3CO)2O(CH_3CO)_2O)
    • Textbook Reference: Chapter 20

  • Ester:

    • General Structure: R−C(=O)−O−RR-C(=O)-O-R (carbonyl group bonded to an alkoxy group)
    • Classification: Ester
    • Example Compound: Ethyl acetate (CH3COOCH2CH3CH_3COOCH_2CH_3)
    • Textbook Reference: Chapter 20

  • Amide:

    • General Structure: R−C(=O)−N(R)2R-C(=O)-N(R)_2 (carbonyl group bonded to an amino group)
    • Classification: Amide
    • Example Compound: Butanamide (CH3CH2CH2CONH2CH_3CH_2CH_2CONH_2)
    • Textbook Reference: Chapter 20

  • Amine:

    • General Structure: R−N(R)−RR-N(R)-R (nitrogen atom with a lone pair bonded to RR groups or hydrogen atoms)
    • Classification: Amine
    • Example Compound: Diethylamine ((CH3CH2)2NH(CH_3CH_2)_2NH)
    • Textbook Reference: Chapter 22

Examples of Common Functional Groups Table 2.1

Practice Problems: Functional Group Identification

  • Structure 1 Identification:

    • Visual Representation:         Lewis structure of ethyl methyl ether
    • Structural Analysis: Contains an oxygen atom single-bonded to two alkyl groups (CH3−CH2−CH_3-CH_2- and −CH3-CH_3).
    • Chemical Formula: CH3−CH2−O−CH3CH_3-CH_2-O-CH_3
    • Identified Functional Group: Ether

  • Structure 2 Identification:

    • Visual Representation:         Lewis structure of butane
    • Structural Analysis: A straight 4-carbon alkane chain consisting exclusively of single carbon-carbon and carbon-hydrogen bonds.
    • Chemical Formula: CH3−CH2−CH2−CH3CH_3-CH_2-CH_2-CH_3
    • Identified Functional Group: Alkane

  • Structure 3 Identification:

    • Visual Representation:         Lewis structure of 1-bromobutane
    • Structural Analysis: A 4-carbon alkyl chain containing a halogen atom (BrBr) attached to the terminal carbon.
    • Chemical Formula: CH3−CH2−CH2−CH2BrCH_3-CH_2-CH_2-CH_2Br
    • Identified Functional Group: Alkyl halide

  • Structure 4 Identification:

    • Visual Representation:         Lewis structure of propanoic acid
    • Structural Analysis: A 3-carbon chain featuring a terminal carbonyl group (C=OC=O) attached directly to a hydroxyl group (−OH-OH).
    • Chemical Formula: CH3−CH2−COOHCH_3-CH_2-COOH
    • Identified Functional Group: Carboxylic acid

  • Structure 5 Identification:

    • Visual Representation:         Lewis structure of 1-butyne
    • Structural Analysis: A 4-carbon chain containing a carbon-carbon triple bond (−C≡C−-C\equiv C-) at position 1.
    • Chemical Formula: CH3−CH2−C≡CHCH_3-CH_2-C\equiv CH
    • Identified Functional Group: Alkyne

Practice Problems: Structural Drawing Instructions

  • a. Cyclohexane:

    • Functional Group Classification: Cycloalkane
    • Structural Characteristics: A six-membered ring of single-bonded carbon atoms, with each carbon attached to two hydrogen atoms.
    • Molecular Formula: C6H12C_6H_{12}

  • b. Amine:

    • Functional Group Classification: Amine
    • Structural Characteristics: Consists of a nitrogen atom bonded to carbon chains or hydrogen atoms (R−NH2R-NH_2, R2NHR_2NH, or R3NR_3N).
    • Representative Example: Diethylamine ((CH3CH2)2NH(CH_3CH_2)_2NH) or Ethylamine (CH3CH2NH2CH_3CH_2NH_2)

  • c. Ester:

    • Functional Group Classification: Ester
    • Structural Characteristics: Contains a carbonyl group (C=OC=O) single-bonded to an oxygen atom which is connected to an alkyl group (R−C(=O)−O−R′R-C(=O)-O-R').
    • Representative Example: Ethyl acetate (CH3COOCH2CH3CH_3COOCH_2CH_3)

  • d. Aldehyde:

    • Functional Group Classification: Aldehyde
    • Structural Characteristics: Features a terminal carbonyl group (C=OC=O) bonded directly to a hydrogen atom (R−CHOR-CHO).
    • Representative Example: Butanal (CH3CH2CH2CHOCH_3CH_2CH_2CHO)

  • e. Ketone:

    • Functional Group Classification: Ketone
    • Structural Characteristics: Features an internal carbonyl group (C=OC=O) bonded to two separate carbon atoms (R−C(=O)−R′R-C(=O)-R').
    • Representative Example: 2-Butanone (CH3COCH2CH3CH_3COCH_2CH_3)

  • f. Alcohol:

    • Functional Group Classification: Alcohol
    • Structural Characteristics: Contains a hydroxyl group (−OH-OH) single-bonded to a saturated carbon atom (R−OHR-OH).
    • Representative Example: 1-Butanol (CH3CH2CH2CH2OHCH_3CH_2CH_2CH_2OH)