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Functional Groups
A functional group is a bond or several bonds in an organic molecule that have certain properties and reactions that are consistent in all molecules containing those sets of bonds
- Functional groups often involve heteroatoms or multiple bonds or both.
- Compounds with multiple functional groups will be classified (and react) as all appropriate functional groups. o CH3CH=CHCH2CH2OH is an alkene and an alcohol o CH 3 CHBrCH2CH2CHO is an aldehyde and an alkyl halide
- Single functional groups are not broken apart into sub-groups o – COOH is a carboxylic acid NOT a ketone and an alcohol o HCOOR is an ester NOT an aldehyde and an ether.
- Functional groups have a strict hierarchy in IUPAC nomenclature and the ending of the name often depends on the highest priority functional group, but functional groups and substituents are NOT the same thing. o Functional groups have distinct reactions, bonds, and properties E.g. an alcohol, an alkene, a nitrile. o Substituents are a way of simplifying molecules for naming. E.g. a methyl group, an ethyl group, an isopropyl group NOTE: Whether alkane is a functional group often depends on whom you ask. Alkanes are often considered to be the basic organic structure and are thus not included as a functional group, but as a skeleton structure common to all molecules. Sometimes alkanes are considered to be a functional group if there is no other functional group in the molecule (e.g. 2,2,3,3-tetramethylbutane is a branched alkane).
Hydrocarbons
Just C and H atoms
Alkane
C C
All C and H All single bonds Unreactive, except with F 2 , Cl 2 , Br 2 , and O 2 Insoluble in water, low boiling points General alkane abbreviated as R Alkene
C C
All C and H At least one C=C double bond Undergo electophilic addition reactions, hydrogenation, and other reactions at the pi bond. Insoluble in water, low boiling points Alkyne
C C
All C and H At least one C-C triple bond Undergo electophilic addition reactions, hydrogenation, and other reactions at the pi bond. Insoluble in water, low boiling points Aromatic (Arene) C and H (possibly N, O, or S) Conjugated, cyclic, planer systems with 4n+2 pi electrons. Undergo electrophilic aromatic substitution reactions. General aromatic abbreviated as Ar
Carbonyls
Class II: attached to C/H
Aldehydes
(Class II) R H
O
C and O double bond with an H on the same carbon. Polar bonds give moderate bp Nucleophilic Acyl Addition Reactions Redox reactions pKa of alpha H 18-20 (enolate reactions) Ketones (Class II)
R R'
O
C and O double bond with two alkyl groups Polar bonds give moderate bp Nucleophilic Acyl Addition Reactions Reduction reactions pKa of alpha H 19-21 (enolate reactions)
Carbonyls Class I: Attached to a heteroatom (leaving group) Carboxylic Acids (Class I)
R OH
O C and O double bond with an OH on the
same carbon. Acidic Hydrogen pka of OH 4- 5 Hydrogen bonds give very high bp. Nucleophilic Acyl Substitution Reactions Reduction reactions Carbonyl Halides (Class I) R Cl O C and O double bond with a halogen on the same carbon. Very reactive with water Nucleophilic Acyl Substitution Reactions Reduction reactions Anhydrides (Class I) R O O O R' C and O double bond with an acid ester on the same carbon. Moderately reactive with water Nucleophilic Acyl Substitution Reactions Reduction reactions Esters (Class I)
R OR'
O C and O double bond with^ an ether on
the same carbon. Nucleophilic Acyl Substitution Reactions Reduction reactions pKa of alpha hydrogens ~25 so can do enolate reactions Amides (Class I)
R N
O
R N
O
H
H
H
R
R N
O
R
R
C and O double bond with an amine on the same carbon. Lots of double bond character in the C- N bond due to resonance. N-H are moderately acidic and can hydrogen bond. Nucleophilic Acyl Substitution Reactions Reduction reactions Nitriles (Class I)
R C N
C and N triple bond. Same oxidation state as Class I carbonyls. Hydrolizes to a carboxylic acid Reduction reactions
Advanced
Imines C
N
C/N double bond. Easily converted to carbonyl in the presence of water. Enols
C
C
OH Formation is unfavored and the diol will
usually revert to the carbonyl unless the alkene forms an aromatic ring
Geminal Diol C
HO OH Not isolable. Formation is unfavored
except with formaldehyde and electron poor carbonyls. Formation catalyzed by acid or base Hemiacetals (^) C HO OR Easily reversed to carbonyl, except with cyclic hemiacetals. Formation catalyzed by acid or base. Acetals (^) C RO OR Formation catalyzed by acid only. Stable and isolable except in the presence of acid.
