functional groups copyright © 2005 by pearson education, inc. publishing as benjamin cummings 1
TRANSCRIPT
Functional groups are• a characteristic feature of organic molecules
that behave in a predictable, similar way. • composed of an atom or group of atoms. • groups that replace a hydrogen atom in the
corresponding alkane.• a way to classify families of organic
compounds.
Functional Groups
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Alkenes and Alkynes
Alkenes contain a double bond between adjacent carbon atoms.(Double bond: 4 electrons)
Alkynes contain a triple bond.(Triple bond: 6 electrons)
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OH- vs -OH
• OH- : hydroxide anion found in bases (e.g NaOH)
• -OH: hydroxyl group colvalently bound to carbon atom in an organic compound
(e.g. ethanol CH3-CH2OH)
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2. Ethers
In an ether, an oxygen atom is bonded to two carbon atoms.
–C–O–C– .
has a common name that gives the alkyl names of the attached groups followed by ether.
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Diethyl ether
3. Aldehydes
An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom.
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acetaldehydeformaldehyde
4. Ketones
In a ketone, the carbon of the carbonyl group is attached to two other carbon atoms.
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Acetone
5. Carboxylic Acids and Esters
Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group.
O ║
— C—OH
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Acetic acid
5. Esters
An ester contains the carboxyl group between carbon atoms.
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Methyl acetate
Organic compounds with Carbon-Nitrogen bonds
1. AminesIn amines, the functional group is a nitrogen atom.
H H
C —N – H or C —N —C
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Methyl amineDimethyl amine
Naming simple amines
• Simple 1º amines are named as “alkylamine”– Examples:
• methylamine CH3NH2
• ethylamine CH3CH2NH2
• butylamine CH3CH2CH2CH2NH2
• Symmetrical 2º or 3º amines are named as
“dialkylamine” or “trialkyamine”– Examples:
• diethylamine (CH3CH2)2NH;
• trimethylamine (CH3)3N
NH3 NH2R NH
R
R
N
R
R
RAmmonia A primary amine A secondary amine A tertuary amine
Examples:
R
R
R
NH2
R
R
R
OH
A primary amine A tertuary alkcohol
NH2
pentan-2-amine
NH2
cyclohexanamine
NH
N-methylcyclohexanamine
Amines are much more polar, than hydrocarbons, especially in acidic conditions
Heterocyclic amines
• Some amines have a nitrogen as part of a ring. These generally have common (non-systematic) names:
NH2
N N
N
N
H
N
N
H
N
H
N
N
HN
aniline pyridine pyrimidine pyrrole
quinoline indole imidazole benzimidazole
Properties of amines
• Amines are moderately polar and are capable of hydrogen bonding.
• Low MW amines (up to about C5) are soluble in water; higher MW amines will dissolve in acidic solution (as their conjugate acid).
• Many amines have foul odors.
• Amines are weak bases.
Example of biologically active amines
H2NCH2CH2CH2CH2NH2 putrescine H2NCH2CH2CH2CH2CH2NH2 cadaverine
H2NCH2CH2CH2CH2NCH2CH2CH2CH2NH2 s permidineH
H2N(CH2)N(CH2)4N(CH2)3NH2 s permineH H
NHCH3
OHH
HO
HO
epinephrine(adrenaline)
NH2
OHH
HO
HO
norepinephrine(noradrenaline)
NH2HO
HO
dopamine
More biologically active amines…
NH2
CH3H
amphetamine(benzadrine)
N
CH2CH2NH2
HO
H
NHCH3
CH3H
methamphetamine (speed)
serotonin
mescaline
NH2CH3O
CH3O
OCH3
N
CO2H
nicotinic acid(niacin)
NN
CH2CH2NH2
H
histamine
More biologically active amines…
H2N C OCH2CH3
O
benzocaine(a topical anesthetic)
Cl
N
N
H
O
O
diazepam (Valium)
N
N
O
NN
CH3
CH2CH2CH3
H
SOO
N
NCH3
CH3CH2O
Sildenafil (Viagra)
Learning Check
Classify each of the following as: alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine or amide.
1) CH3─CH2─CH2─OH
2) CH3─O─CH2─CH3
3) CH3─CH2─NH2
O O ║ ║
4) CH3─C─OH 5) CH3─C─O─CH3
alcohol
ether
amine
carboxylic acid ester
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Organic compounds with
Carbon-Oxygen bonds1. Alcohols
An alcohol contains the hydroxyl (-OH) functional group.(instead of an H in that place)
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Ethanol
Alcohols
An alcohol contains a hydroxyl group (—OH) attached to a carbon chain.
A phenol contains a hydroxyl group (—OH) attached to a benzene ring.
water alcohol phenol
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Naming Alcohols
The names of alcohols• in IUPAC replace the -e with -ol.• with common names use the name of the alkyl group followed by alcohol.
Formula IUPAC Common Name
CH4 methane
CH3─OH methanol methyl alcohol
CH3─CH3 ethane
CH3─CH2─OH ethanol ethyl alcohol
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Classification of alcohols is• determined by the number of alkyl groups attached to
the carbon bonded to the hydroxyl.• primary (1°), secondary (2°), or tertiary(3).
Primary (1º) Secondary (2º) Tertiary (3º)1 group 2 groups 3 groups H CH3 CH3
| | | CH3—C—OH CH3—C—OH CH3—C—OH
| | | H H CH3
Classification of Alcohols
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Properties of Alcohols and Ethers
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Boiling Points of Alcohols
Alcohols• contain polar OH
groups. • form hydrogen bonds
with other alcohol molecules.
• have higher boiling points than alkanes and ethers of similar mass.
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Boiling Points of Ethers
Ethers• do not have a polar
group.• have an O atom,
but there is no H attached.
• cannot form hydrogen bonds between ether molecules.
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Solubility of Alcohols and Ethers in Water
Alcohols and ethers • are more soluble in water than alkanes because the
oxygen atom can hydrogen bond with water.
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