Download - Chem 1152: Ch. 16

Chem 1152: Ch. 16

Amines

NitrogenNitrogen• Mostly inert gas (N2) under standard conditions

• ~78% of atmosphere• Found in:

– Ammonia (NH3)

– Nitrates (fertilizers)– Nitric acid (HNO3)

– Propellants (N2O, nitrous oxide)

– Explosives (nitroglycerine)– Cyanides (CN-)

• 4th most abundant element in human body• Critical to building blocks of life/CNS function

– Proteins– DNA– RNA– Neurotransmitters

R

O

O-

NH3+

Amino acid

nitroglycerine

AminesAmines• Organic derivatives of ammonia• One or more H atoms replaced by aromatic or alkyl group

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

ammonia

Primary (1°) Secondary (2°) Tertiary (3°)

H

HH

N:

R O

R R

HR O

R H

HR O

H H

Halcohols

R

HH

N

R

HR

N

R

RR

N: : :

R-OH

Naming Amines – Common NamesNaming Amines – Common Names• Common names• For low MW amines• Alphabetically link names of alkyl or aromatic groups bonded to nitrogen, attach suffix –amine.

H

HCH3N CH3

H

CH3N

CH3

CH3CH3N

methylamine ethylmethylamine trimethylamine

H

CH3N

CH3

H

H

N

propylaminemethylphenylamine

Naming Amines – IUPAC NamesNaming Amines – IUPAC Names• Replace –e in alkane with –amine.• Number position of amino group lowest on parent chain.• If substituent on nitrogen, prefixed with N.

NH2

CH3CH3

NH2

CH3

CH3

CH3NH

CH3CH3

NH2

CH3CH3

CH3NH

CH3CH3

CH3 CH3N

CH3CH3

CH3CH3

N

CH3CH3

NH2

NH2

CH3CH3

NH2

Naming Amines – IUPAC NamesNaming Amines – IUPAC Names• Replace –e in alkane with –amine.• Number position of amino group lowest on parent chain.• If substituent on nitrogen, prefixed with N.

3-Pentanamine

NH2

CH3CH3

3-Methyl-1-butanamine

NH2

CH3

CH3

CH3NH

CH3CH3

N-Methyl-2-butanamine

NH2

CH3CH3

2-Hexanamine

CH3NH

CH3CH3

CH3 CH3N

CH3CH3

N-Methyl-2-hexanamine N,N-Dimethyl-2-hexanamine

CH3CH3

N

CH3CH3

NH2

NH2

CH3CH3

NH2

N-Ethyl-N-methyl-2-hexanamine 2,5-hexanediamine cyclohexylamine

Naming Amines – AromaticsNaming Amines – Aromatics

aniline 3-Ethylaniline

N-Ethyl-N-methylaniline

2-Methylaniline

• Usually named as substituted anilines• For groups on N of aniline, identify with N to indicate not attached to

ringNH2

CH3

NH2CH3

NH2 CH3NH

N-Ethylaniline

CH3

CH3N

CH3

CH3N

N,N-dimethylaniline

H

N

diphenylamine

CH3

H

CH3N

2-Ethyl-N-methylaniline

CH3

CH3

H

N

N-Ethyl-2-methylaniline

NH2

CH3 CH3

3-phenyl-2-heptanamine

Physical Properties of AminesPhysical Properties of Amines• 1° and 2° amines form H-bonds among themselves• Bonds weaker for amines than alcohols (EN of oxygen > nitrogen)

• BP’s of 1° and 2° amines lower than alcohols of comparable MWH

CH3 O H

CH3

O

alcohol amine

• Amines with fewer than 6 C’s (1°, 2° and 3°) soluble in water due to H-bonding

• Amines stink!• Low MW amines smell like ammonia• Higher MW amines smell like rotten fish

NH2NH2

NH2NH2

putrescine

cadaverine

Chemical Properties of AminesChemical Properties of Amines• Basicity: Amines are weak bases

From Brønsted-LowryBase accepts proton and becomes a conjugate acid

Chemical Reactions of AminesChemical Reactions of Amines• Amines reversibly react with water, form hydroxide ions

RNH2 + OH2 + OH

-

RNH3

+

+ OH2 + OH-CH3

NH2

CH3

NH3+

• Amines form salts when they react with acids

RNH2 + ClH Cl

-

RNH3

+

+ ClHCl-

CH3

NH2

CH3

NH3+

+ OH

O

CH3

CH3

CH3

NH2

CH3

CH3

NH3+O-

O

CH3

Amine SaltsAmine SaltsNaming: Change amine to ammonium and add name of negative ion derived from acid

HCH3

CH2CH3

CH3

N+

Ethyldimethylamine (common)

N,N-dimethylethanamine (IUPAC)

BrCH3

CH2CH3

CH3

N+

ethyldimethylammonium bromide

• Amine salts are white crystalline solids with high MP’s.• Amine drugs usually given in form of salts to improve their ability to

dissolve in body fluids


ethyldimethylammonium

Amine SaltsAmine SaltsAmine salts are pH dependent, like CA’s.

H

R

H

H N+

R

H

H NH+

OH-

amine(high pH)

amine salt(low pH)

Amine salts may have 4 alkyl/benzene groups quaternary ammonium salts

Acetylcholine is important QA salt involved in transmission of nerve impulses

Some QA salts have antiseptic qualities that kill bacteria and fungii. e.g. benzalkonium (Zephiran) chloride used by physicians to scrub before

surgery and to sterilize instruments


R

HH

N

AmidesAmidesAmides are combination of CA and ammonia or amine joined by amide linkage.

H

H

R

O

N

Ammonia or amine

Amide linkage

RR

O

O

Carboxylic AcidCarboxylic Acid

AlcoholEster linkage

Amide Ester

Not formed by reaction between CA and amine (produces salt)

+ OH

O

CH3

CH3

CH3

NH2

CH3

CH3

NH3+O-

O

CH3

Amines Form AmidesAmines Form Amides Amides are formed through reaction of primary and secondary amines

with acid chlorides and acid anhydrides. Similar to esterification reactions.


Amide ReactionsAmide Reactions

O O

CH3 O CH3+

CH3

NH2

O

OH CH3CH3

NH

O

CH3

+

O O

CH3 O CH3+

CH3

CH3

NH

O

OH CH3+

CH3

CH3

N

O

CH3

O O

CH3 O CH3+

CH3

CH3

CH3

N No Rxn

O

CH3 Cl+ CH3NH2

O

Cl + CH3CH3NH

+CH3NH

O

CH3ClH

CH3

CH3O

N + ClH

Synthesis of NylonSynthesis of Nylon


CarpetingClothingMedical tubingSuturesParachutes

Aspirin SubstitutesAspirin Substitutes


Acetylsalicylic acid

AspirinPain relieverFever reducerAnti-inflammatory

Harmful side effectsAllergic reactionsGastrointestinal bleedingCan induce Reye’s syndrome in children

AcetaminophenPain relieverFever reducerDoes not irritate intestinal tractNegativesNot an anti-inflammatoryOveruse can lead to liver and kidney damage

Amines as NeurotransmittersAmines as Neurotransmitters


Neurotransmitters: Molecules that carry chemical messages between neurons in nervous systemreleased into synapse (gap between synaptic terminal of one neuron and Dendrite of another) in response to electrical signalDiffuse across synapse and bind to receptors on dendrites of next neuron

neur

on

Amines as NeurotransmittersAmines as Neurotransmitters


In CNS (brain and spinal cord), the most important neurotransmitters are amines: Acetylcholine Norepinephrine Dopamine Serotonin

In addition to being chemical messengers, some neurotransmitters may also be partly responsible for moods, mental illness

Amines and Mental IllnessAmines and Mental Illness


Neurotransmitters dopamine and norepinephrin both derived from tyrosine Tyrosine essential AA obtained from diet (egg whites, turkey, soy)

Norepinephrine and epinephrine (adrenaline) act as drugs related to fight or flight response

directly increasing heart rate triggers the release of glucose from energy stores increases blood flow to skeletal muscle increases the brain's oxygen supply

Excess norepinephrine (NE) results in feelings of elation Low NE levels may cause depression

Amines and Mental IllnessAmines and Mental Illness


Derived from the AA tryptophan, another essential AA obtained from diet Influences sleeping, regulation of body temp., sensory perception May be related to mental illness

AmphetaminesAmphetamines


Amphetamines structurally and chemically similar to adrenaline Raise glucose level in blood Increase pulse rate Increase blood pressure

May be legally prescribed to elevate mood or reduce fatigue Street names:

Bennies, pep pills, Reds, red devils, speed, dexies, uppers

AlkaloidsAlkaloids


Weakly basic amines derived from plants

Stimulate CNS/Resp. systems Treatment of malaria

CNS Depressants, used as painkillers Morphine derivative

Naming AmidesNaming Amides• Simple amides named after corresponding carboxylic acids

by changing –ic or –oic of acid to –amide.• Common names are used more often than IUPAC names.

formic acid

H

O

OH H

O

NH2

Common nameIUPAC name methanoic acid

formamidemethanamide

acetic acidCommon nameIUPAC name ethanoic acid

acetamideethanamide

CH3

O

OH CH3

O

NH2

benzoic acidCommon nameIUPAC name benzoic acid

benzamidebenzamide

O

OH

O

NH2

Naming AmidesNaming Amides• Simple amides named after corresponding carboxylic acids by changing –ic or –

oic of acid to –amide.• Common names are used more often than IUPAC names.• Use italicized capital N to identify alkyl groups bonded to nitrogen.

N-methylformamideCommonIUPAC

CH3H

O

NH

N-methylmethanamide

CH3

CH3CH3

O

N

N,N-dimethylacetamideN,N-dimethylethanamide

CH3

CH3O

N

N-ethyl-N-methylbenzamide

N-ethyl-N-methylbenzamide

Naming AmidesNaming Amides• Simple amides named after corresponding carboxylic acids by changing –ic or –

oic of acid to –amide.• Common names are used more often than IUPAC names.• Use italicized capital N to identify alkyl groups bonded to nitrogen.

N,N-diethylethanamide

CH3

CH3

CH3

O

N

CH3

CH3CH3

H

O

N

N-isobutylbutanamide

CH3

O

N

N-ethyl-N-phenylbenzamide

CH3

CH3

O

NH

2,N-dimethylbenzamide

Physical Properties of AmidesPhysical Properties of Amides• Unsubstituted amides can form complex networks of

intermolecular H-bonds– Increases MP’s of these substances

• Increasing the number of substituents on amide reduces H-bonding– Reduces MP’s and BP’s

• Amides do form H-bonds with water– Increases solubility


Amide HydrolysisAmide Hydrolysis• Most important rxn is hydrolysis• May involve either acid or base• One of the products will always be a salt


Amide HydrolysisAmide Hydrolysis



O

CH3 NH2+ HOH + ClH

HeatO

CH3 OH NH4+Cl-+

acetamide Acetic acid Ammonium chloride

+ HOH + ClHHeat

CH3

O

CH3 NH

O

CH3 OH Cl-+ CH3 NH3

+

N-methylacetamide Acetic acid methylammonium chloride

+Heat

CH3

O

CH3 NHOHNa

O

CH3 O-

NH2CH3+Na

+

N-methylacetamide Sodium acetate

methylamine


N-ethylbenzamide Benzoic acid Ethylammonium chloride

+ HOH + ClHHeat

CH3O

NH

Cl-+

CH3

NH3+

OH

O

+Heat

CH3O

NH

OHNa +CH3

NH2

O-

O

Na+

N-ethylbenzamide Sodium benzoate

Ethylamine