AMINES
amines: org cpds derived from ammonia by substitution of H atoms in ammonia by alkyl / aryl groups
Formula: C_nH_2n+1NH₂ (n=1,2,..) (alkyamine)
functional group: amino group, -NH₂

Formation
Aliphatic 1° amine
-Reduction of alkanonitrile / amide
reagent: LiAlH₄ in dry ether
condition: ice-cold temp (<10°C)
R-CN + 4[H] >(LiAlH₄ in dry ether, ice-cold temp)> R-CH₂NH₂
R-C(=O)NH₂ + 4[H] >(LiAlH₄ in dry ether, ice-cold temp)> R-CH₂NH₂ + H₂O
Aromatic 1° amine
reagent: Fe filings, conc HCl
condition: heat under reflux
C₆H₅-NO₂ + 6[H] >(Fe, conc HCl, heat, reflux)> C₆H₅NH₂ + 2H₂O

Physical properties
-1° amines; lower members- gases at rtp (methyl + ethylamine) (phenylamine: colourless liquid: readily > brown due to air oxidation)
-higher than expected mp + bp (intermolecular H-bonds)
-1° amines; lower members(C₁-C₅)- soluble in water [intermolecular H-bonds & chemical reaction bet amine + water molecules: R-NH₂ + H₂O > RNH₃⁺ + OH^- (OH^-: gives alkaline properties of amine)]

Basic properties
reagent: dil HCl
condition: room temp
R-NH₂ + HCl > R-NH₄⁺Cl^-
(free amine can be obtaind by adding NaOH to the alkylammonium salt; R-NH₃⁺Cl^- + NaOH > R-NH₂ + NaCl + H₂O)

Structural infuence on basic strength of amines
amines = bases as can donate e^- pair of N atom to proton(H⁺) of water to form alkylammoium ion + OH^-
R-NH₂ + H₂O > R-NH₃⁺ + OH^-
electron donating group; pushes e^-s towards N atom > lone e^- pair readily protonated > more alkylammonium cation + OH^- > more basic
electron withdrawing group; pulls e^-s away from N atom > lone e^- pair less readily protonated > less alkylammonium cation + OH^- > less basic
basicity: depends by OH^- conc = [OH^-], higher [OH^-] > more basic (k_b: base dissociation constant- lower k_b > less basic)
ammonia, NH₃; k_b = 1.8×10^-5
ethylamine, CH₃CH₂NH₂; k_b = 5.4×10^-4
phenylamine, C₆H₅NH₂; k_b = 5×10^-10
phenylamine less basic than ammonia as N lone pair partly delocalised in benzene ring > less available for protonation

Alkanoylation
reagent: alkanoyl chloride
condition: room temp
equation: R-NH₂ + Cl-C(=O)-R' > R-NHC(=O)-R' +HCl

w/ nitrous acid
reagent: -sodium nitrite, NaNO₂, -dil HCl
condition: < 5°C (ice-cold temp)
aliphatic 1° amine
equation: R-NH₂ + HNO₂ >(NaNO₂/dil HCl, <5°C)> R-OH + N₂ + H₂O
aromatic 1° amine = diazotisation (HCl- 2mol/dm³)
equation: NH₂ + HNO₂ + HCl >(NaNO₂/dil HCl, <5°C)> + 2H₂O

Formation of azo dye
the coupling reaction w/ phenolic cpds to form azo dye
diazonium ion = electrophile > reacts w/ another bezene ring, eg phenolic cpds > brightly coloured cpds = azo dye
azo dye colour from extensive delocalisation of valence e^-s from 1 benzene ring through the -N=N- group to the next benzene ring (delocalisation of e^-s: absorb violet, blue, green light > azo dye usually red, orange/ yellow)

[diazonium ion attaches to 2/4/6 position of phenol during electrophilic subs]

Formation of phenol
benzene diazonium ion diluted w/ water and boiled > phenol
C₆H₅NN⁺Cl^- + H₂O >(boiled under reflux)> C₆H₅OH + N₂ + HCl

Distinguihing aromatic 1° amine & aliphatic 1° amine

TEST	phenylamine (aromatic)	phenylmethylamine (aliphatic)
+ Br2(aq), room temp	white ppt	no reaction
+ NaNO2 & dil HCl at 5°C, + phenol	orange azo dye formed	bubbles of nitrogen gas, no reaction w/ phenol

AMINO ACIDS
MF; aminoalkanoic acid
functional group: -carboxyl(-C(=O)OH) + -amino(-NH₂) groupp
about 20 naturallly occuring 2-amino acids (-amino acids) where -C atom adjacent to -C(=O)OH

Physical properties
-amino acids = crystalline (s) w/ high mp & soluble in water (not in inorganic solvents) [strong intermoelcular bonds bet lattice particles]
solid amino acids: lattice particles = zwitterions (or dipolar ions) attracted by ionic bonds


Acidic & basic properties; zwitterion formation
neutral sol + solid state: amino acid = dipolar ion (zwitterion)

zwitterion formed from internal acid-base reaction: -C(=O)OH group donates H+ to -NH₂ group > diff pH: diff ion
neutral (pH 7)
acidic (pH 2.5)
alkaline (pH 10)

Electrophoresis of amino acid: movement & separation of charged subs in elec field
 amino acids:
 -pH 7; no movement ,
 -pH 3; towards -ve electrode
 -pH 11; towards +ve electrode

Reactions of carboxyl group
-Estereification


-Neutralisation
NH₂CH[]C(=O)OH + NaOH > NH₂CH[]C(=O)O^-Na⁺ + H₂O

Reactions of amino group
-w/ nitrous acid
NH₂CH[]C(=O)OH + HNO₂ >(NaNO₂/dil HCl, < 5 °C)> HOCH[](=O)OH + N₂ + H₂O

-alkanoylation
NH₂CH[]C(=O)OH + ClC(=O)R > RC(=O)NHCH[](=O)OH + N₂ + HCl

-neutralisation
NH₂CH[]C(=O)OH + HCl > Cl^-+NH₃CH[](=O)OH

PROTIEN
protien = long-chained natural polymers from 2-amino acids, ~20 amino acids in nature, several 1000 units > RMM: 10⁴-10⁷

Peptide link-formed through a condensation reaction: 2 amino acids join together w/ the removal of an H₂O molecule (-OH from carboxyl group and -H of amino group of another amino acid molecule removed)
(a dipeptide:cpd w/ 1 peptide link formed from 2 amino acids, tripeptide: 2 peptide links, 3 amino acids)


Structure of protein

protein = polypeptide w/ > 40 amino acid residues (units) joined by peptide links/bonds through a condensation reaction (reaction w/ removal of H₂O molecule)

Hydrolysis of protein

peptide link (amide bond) in proteins hydrolysed by acid / alkali > constituent amino acids (separated by paper chromatography, amino acids- colourless > detected by locating agent, eg Ninhydrin which colours amino acids blue / violet)

Biological importance of proteins
proteins = chief constituent in building materials of living cells
-enzymes for metabolism
-haemoglobin for red blood cells to carry O₂
-DNA, RNA & nucleic acids for genetic control
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