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Amines
- bases, substituted ammonia
- biologically significant: amino acids, DNA, RNA bases, alkaloids
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General formula for primary amine
R-NH2
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General formula for secondary amine
R2-NH
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General formula for tertiary amine
R3-N
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General formula for quaternary
R4-N+X-
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More information on amines
- organic derivative of ammonia (NH3) in which 1 or more hydrogen atoms have been replaced by an alkyl, acycloakly, or an aryl group (beneze ring)
- N has 5 valence e-, 3 covalent bonds, and 1 nonbonding electron pair
- N is also less electronegative than O
- N is one of the elements involved in the formation of H+ bonding
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Properties of amines
- N is very electronegative (although less than O)
- Results in:
- -N-H bond being very polar
- -hydrogen bonding being possible
- -high boiling points
- -amines being organic bases
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Classification of amines
- determined by the number of carbon atom directly boned to the N atom
- classified as: primary, secondary, or tertiary
- Note: t-butyl alcohol is a t-alcohol, while t-butyl amine is a primary amine
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Causes of isomers in amines
- different carbon atom arrangements produce isomers
- different positioning of the nitrogen atom on a carbon chain
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Causes of isomers for secondary and tertiary amines
- different partititioning of carbon atoms among the carbon chain
- ex: CH3CH2NHCH2CH3- diethyl amine
- CH3NHCH2CH2CH3- methylpropyl amine
- CH3NHCH[2(CH3)]
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Amine nomenclature
- Both common and IUPAC names are used
- Simple amines are named by listing the alkyl group or groups attched to the N atom in alphabetical order and adding the suffix -amine
- appears as 1 word
- prefix di and tri are used when identical groups are bonded to the N atom
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Naming diamines
- in diamines the final -e of the carbon chain is retained
- ex.1,4- butanediamine
- NH2CH2CH2CH2CH2NH2
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Nomenclature of secondary & tertiary amines
- treat additional branches as a substituent on the nitrogen
- base name is based on longest chain that contains the amine
- name other chain as alkyl substituent of the N
- use N- at front of a branch name to indicate that substituant is on the nitrogen
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Naming aromatic amines
- aniline is the simplest aromatic amine
- compounds are named as substituted anilines
- anitalic "N" is used to indicate that an alkyl group is attached to the nitrogen and not to the ring
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Physical properties of amines
- methylamines and ethylamines are gases at room temp & have ammonia like odor
- most other amines are liquid & have odor resembling fish
- have the ability to form H-bonding
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Boiling points of amines
boiling points are intermediate b/w those of alcohols and alkenes of similar molecular masses
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solubility of amines
low molecular mass amines are very soluble in water
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Amines+acid--->
- amines+acid--->salt
- ex. R-NH2+HCl---> R-NH3+ + Cl-
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Basicity of amines
NH3 + water---> NH4+ + OH-
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Basicity of amines generalizations
- substituted ammonia ions are always charged species rather than neutral molecules
- N atom in the structure participates in 4 bonds
- substituted ammonium ions have common names derived from the names of the "parent" amines w/ the words ammonium ion replacing amine
- -examples in notes
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Production from ammonia and an alcohol uses:
Al2O3 & heat
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Preparation of amines:
ammonia + alkylhalide in the presence of a base
ex.ammonia+ ethyl bromide+ sodium hydroxide--->aminoethane+sodiumbromide+water
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Preparation of amines:
amine+water--->
amine+water---> ammonium ion+hydroxide
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Preparation of amines:
amine salt+base--->
amine salt+base--->amine+salt+water
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Neutralization formula of an amine
- RNH2+HCl--->RNH3+ Cl-
Note: no H2O os produced in this reaction - Amine salts are the only product
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Neutralization
- 1.salts exist as white crystalline solids
- 2.reliatively high melting points
- 3.salts are always more soluble
- 4.many drugs are prepared and administered as salts b/c of their solublitiy
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General formula for amides
R-C(=O)NH2
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amide nomenclature
drop -e ending and replace w/ -amide
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Amide formation
amines react w/ acid chlorides or acid anhydrides to form amides
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Preparation of amides
production from a carboxylic acid uses:
NH3 & heat
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