NITROGEN COMPOUNDS

1. Physical properties
   1. 1.Smell

      Nota:

      • increasingly pungent as molecular weight increases
   2. 2. Boiling point

      Nota:

      • -among isomeric amines: (in order of increasing bp) primary amine > sec > tertiary this is due to difference in no. of N-H bond present (hydrogen bonding), where tertiary has none and only contains pdpd interactions which are weaker than hydrogen bonds thus requiring less heat to overcome bonds
      • Between compounds with similar electron cloud size: 1) compare types of intermolecular bonds Alcohol, Amine > Alkane This is because alcohol and amine participates in hydrogen bonding while alkane only contains dispersion forces which are much weaker hydrogen bonds thus less heat needed to overcome bonds 2) Compare polarity of hydrogen bond Alcohol > Amine As O-H bond is more polar than N-H bonds
   3. 3. Solubility

      Nota:

      • -Lower aliphatic amines (6-7 C) are readily soluble in water due to ability to form strong hydrogen bonds with water molecues - amines of larger molecular weight are virtually insoluble in water due to large hydrocarbon skeletons which are non polar
   4. 4. Basicity

      Nota:

      • Depends on: 1. Stability of conjugate acid 2. Electron density of N atom
      • Secondary amide > primary amide -This is because of presence of electron withdrawing alkyl groups, which increases electron density of N atom, allowing its lone pair of electrons to be more available for donation to acid to form dative bond with proton Tertiary amide differ from this trend even though it has highest amount of alkyl groups. This is because it is less effectively solvated through hydrogen bonding with water molecules as compared to pri and sec amine
2. Reactions

   Nota:

   • 1-3 for both amine and phenylamine
   1. 1. With acids (as a base)

      Nota:

      • -one product only (ionic) i.e. CH3NH2 + HCl -> CH3NH3+Cl- -salts are soluble in aqueous solutions. Salts (white crystalline solids) obtained when the aqueous solution is evaporated -salts are ionic, soluble in water not organic solutions
      • Amines can be separated from other organic compounds by converting it into a water soluble ammonium salt by this reaction 
   2. 2. With halogenoalkanes (as a nucleophile)

      Nota:

      • Conditions: halogenoalkanes, heat in sealed tube mechanism same as reaction 1 under synthesis (actually it's the 'further substitution' part of that reaction)
   3. 3. With acyl chloride (as a nucleophile)

      Nota:

      • Condition: acyl chloride - Primary and secondary amine forms amide - Tertiary cannot undergo this reaction due to lack of hydrogen atoms
   4. 4. With aqueous bromine (for phenylamine only)

      Nota:

      • -Electrophilic subsitution: 2,4,6 directing (look at attached image HAHAHAH) -Conditions: aq bromine -Observations: Yellow orange solution decolourise, white ppt formed 
      • Comments:  - Lewis acid catalyst not needed unlike bromination of benzene. This is because lone pair on N atom delocalises into benzene ring, increasing ring's electron density, making it much more succeptible to electrophilic attackthan benzene .
3. Synthesis
   1. 1. From nucleophilic substitution of halogenoalkane

      Nota:

      • NH3 + RX -> RNH2 + HX Conditions:  1) ethanolic concentrated NH3,  2) heat in sealed tube Comments:  a) Further substitution can occur if there is excess halogenoalkane as amide formed also contains N atom with lone pair which can act as nucleophile. b) Further substitution can be prevented with use of excess concentrated NH3 (favour primary amine formation)
   2. 2. From reduction of nitriles

      Nota:

      • RCN + 4[H] -> RCH2NH2 Conditions: 1) Organic nitrile 2) LiAlH4 in dry ether OR H2 / Ni with high temp and pressure
   3. 3. From reduction of nitrobenzene (phenylamine produced)

      Nota:

      • nitrobenzene + 6[H] -> phenylamine + 2H2O Conditions:  1) Sn in concentrated HCl/ heat under reflux 2) dilute NaOH (aq) [strong base used to liberate amine]
4. -NH2

Nota:

• --CONH2

1. Physical properties
2. Synthesis
   1. From acyl chloride

      Nota:

      • RCOCl + NH3 / RNH2 / RNHR' -> amide + HCl Conditions: with ammonia or primary / sec amine (in excess) which acts as nucleophiles Conditions: must be nucleophilic and must also possess a hydrogen atom
3. Reactions
   1. Hydrolysis by aqueous acid or bases

      Nota:

      • Conditions: Dilute acid or base, heat 1. Acid hydrolysis  -with primary amide: RCONH2 + H2SO4 -> RCOOH + NH4+ 2. Alkaline hydrolysis -with primary amide: RCONH2 + NaOH -> RCOO-Na+ + NH3 - with substituted amides: RCONHR' + NaOH -> RCOO-Na+ + RNH2
      • refer to photo for mechanism (for substituted amides) but i think don't need to know 
4. -CONH2
5. 2. Boiling point

   Nota:

   • Relatively high boiling points due to presence of extensive intermolecular hydrogen bonding resulted from polar nature of N-H bond
   1. 3. Solubility

      Nota:

      • Simple amides extremely soluble in water due to ability to form extensive hydrogen bonds with water
   2. 4. Basicity

      Nota:

      • Neutral solution produced -lone pair of electron on N atom not available for donaion to acid due to delocalisation of the electron lone pair over the C=O bond

1. General stuff

   Nota:

   • -α amino acids => naturally occuring amino acids -20 different α amino acids -all chiral except glycine
2. Chemical properties

   Nota:

   • 1) Undergoes intramolecular acid base reaction -> form zwitterions 2) Can be separated by electrophoresis, where distance migrated ∝ (charge / mass)
   1. Protonated (NH3+)
   2. Electrically neutral (zwitterion)
   3. Deprotonated (COOH-)
3. Physical properties

   Nota:

   • a) Crystalline solids at rtp b) High melting points due to strong ionic bonds between dipolar zwitterions c) Solid lattice structure d) Soluble in water (less soluble in organic solvents) due to strong ion dipole interactions between zwitterions and water molecules
4. Peptide bond formation

   Nota:

   • via condensation reaction (loss of H2O)

1. Chemical properties
   1. 1. Hydrolysis into amino acids

      Nota:

      • Affects primary structure only
   2. 2. Denaturation

      Nota:

      • -Breaking down of secondary, tertiary and quaternary structure of protein (primary structure not affected), causing change in conformation and loss in protein function   - Changes irreversible
      1. i. Heat
         1. iv. Detergent
      2. ii. pH changes
         1. v. Heavy metals
      3. iii. Mechanical agitation
         1. vi. Oxidizing and Reducing agents
2. Structure
   1. Primary
   2. Secondary
   3. Tertiary
   4. Quatenary
3. Functions

   Nota:

   • 1. Enzymes 2. Antibodies 3. Transport proteins 4. Regulatory proteins 5. Structural proteins 6. Movement proteins 7. Nutrient proteins