Common Organic Questions

• non-polar, does not attract nucleophiles and electrophiles • C−C and C−H bonds intermolecular covalent bonds very strong, ↑ e needed to overcome nucleophiles & electrophiles are polar

carbonyl carbon is polarised by highly electronegative oxygen atom causing the carboxyl carbon to be electron deficient able to react with hydride nucelophile C=C in alkene is not polarised, does not have electron deficient sites to react with hydride nucleophile

• structure: simple molecular structure & non polar • imf: id-id • ↑length of chain: e- cloud larger & more polarisable → more e needed to overcome stronger id-id →↑bp • branching: smaller surface area of contact for id-id interaction → ↓e required to overcome weaker & less extensive id-id in alkane

• two different groups of atoms are bonded to each of the C atoms involved in the C=C • restricted rotation of C=C due to the presence of pi bonds

• has activating group: ↑ electron density of the ring → ↑ susceptible to electrophilic attacks • has deactivating group: ↓ electron density of the ring → ↓ susceptible to electrophilic attacks

• addition reactions will cause the disruption of delocalised pi electrons cloud • causing benzene to lose the resonance stability

• structure: simple molecular, polar • imf: id-id & pd-pd • ↑length of chain: e- cloud larger & polarisable → more e needed to overcome id-id • comparison b/w different halogens: e- cloud increases from Cl to I, e- cloud more polarisable, id-id stronger, more e needed to overcome do not mix up boiling point with C-X bond strength for nucleo sub!!!

• bond strength of the C – X ↓ from Cl to Br to I: • effectiveness of the orbital overlap between the C atom and halogen atom decreases as • size of valence orbital increases from Cl to I • nucelophilic substitution increases from Cl to I OR • electronegativity of the halogen atom X decreases from chlorine to iodine • ionic character of the C–X bond to decrease down the group bond strength used for attack of nucleophile not for boiling point!

• delocalisation of lone pair of e- on halogen atom into the benzene ring • resulted carbon–halogen bond having partial double bond character • stronger and more difficult to break • rear side of the carbon–halogen bond blocked by benzene ring • pi electron cloud of benzene ring repels the lone pair of e- of incoming nucleophile

aromatic character is destroyed and benzene ring becomes unstable as it is no longer resonance stabilised

• HCN undergoes partial dissociation in water, does not form CN- nucleophile readily • KCN undergoes complete dissolution in water to form the CN- nucleophile needed in the rate-determining step of the nucleophilic addition reaction. Also, the acidic condition provides the H+ ions required for the protonation of intermediate to form the hydroxynitriles.

• Favoured by stability of carbocation formed from tertiary halogenoalkane SN2 favoured: tertiary halogenoalkane, greater steric hindrance, hinder backside attack of nucleophile SN1 favoured: (more e- donating grp) * rate of formation of carbocation: - ↑ e- donating grp disperse +ve charge of carbonation - carbocation stabilised and formed faster * strength of carbon-halogen bond: * down grp 17, size of atom increase, valence orbital becomes larger and more diffused, less effective overlap, less E needed to break the weaker carbon halogen bond​ step 1 forms carbocation

SN2 preferred: * Primary Halogenoalkane, less steric hindrace * backside attack of nucleophile not hindered SN1 less preferred: primary carbocation formed unstable as only one electron-donating alkyl group to disperse the positive charge * strength of carbon-halogen bond: * down grp 17, size of atom increase, valence orbital becomes bigger and more diffused, less effective overlap, less E needed to break the weaker carbon halogen bond​ ​​​​​​​

• carbocation arranged in trigonal planar • allows of nucleophilic attack from both side of the plane with equal probabilities • equal amt of 2 enantiomers of product formed • two enantiomers rotate plane polarised light to an equal angle in opposite direction, → forms racemic mixture, rotation is cancelled out

• structure: simple molecular, polar • imf: id-id, pd-pd, H2 bond • intermolecular hydrogen bond (↑bp) • no. of OH grps: extensiveness of the intermolecular hydrogen bonding ↑, ↑ e needed to overcome stronger h2 bond • have intramolecular hydrogen bonds: limits the number of sites available for intermolecular hydrogen bonding (↓bp) • ↑length of chain: e- cloud larger & polarisable → more e needed to overcome id-id • linear: more extensive id-id between its molecules

• delocalisation of lone pair of e- on oxygen atom into the benzene ring • resulted C-O bond having partial double bond character • stronger and more difficult to break • rear side of the carbon–oxygen bond blocked by benzene ring • pi electron cloud of benzene ring repels the lone pair of e- of incoming nucleophile

alcohol weaker: * electron-donating alkyl grp * intensify -ve charge on O atom of alkoxide ion * alkoxide destabilised, alchol dissociates to a smaller extent, producing less H+ phenol stronger: * p-orbital of oxygen overlaps with the pi-electron cloud of the benzene ring * -ve charge on the oxygen atom of the phenoxide ion delocalised into benzene ring * phenoxide stabilised as charge is dispersed * phenol dissociates to a greater extent, producing more H+ more stable to congugate base, stronger the acid

• aldehyde has 1 e- donating grp, ketone has 2 e- donating grp • partial positive charge on the carbonyl carbon in ketone dispersed to greater extent • ketone less electron deficient and less susceptible to nucleophilic attack • additional bulky -CH3 grp ↑ steric hindrance about the carbonyl carbon in ketone • hinders the approach of the attacking nucleophile

• structure: simple molecular, polar • imf: id-id, pd-pd, H2 bond • intermolecular hydrogen bond (↑bp) (compare with alcohols) • H2 bond stonger in carbo acid as OH grp is more polarised due to e- withdrawing C=O grp • ↑length of chain: e- cloud larger & polarisable → more e needed to overcome id-id • linear: more extensive id-id between its molecules

• H atom bonded directly to N, O or F in one molecule • N, O or F with a lone pair of electrons in another molecule. N,O,F are highly electronegative atoms O have partial -ve charge, H have partial +ve charge, draw H2 bond connecting the lone pair of e- on O to H atom

• state interactions: * id-id b/w R grps of acid and H2 bond b/w COOH grp (solute-solute) * H2 bond b/w water molecules (solvent-solvent) * H2 bond b/w COOH grp and water molecules (solute-solvent) • As length↑, id-id b/w R grps of acid more significant, interferes with H2 bond b/w water molecules • interactions b/w water and acid becomes more predominantly id-id (initially it was more predominantly h2 bond with water) • e released when forming id-id with water insufficient to overcome H2 bond with water and more predominant id-id b/w acid molecules

alcohol: * e- donating alkyl grp intensify -ve charge on O atom in alkoxide ion * alkoxide ion least stable, alcohol least acidic phenol: * resonance stabilised STAR!! * p-orbital O overlap with pi e- cloud of benzene, -ve charge of O delocalise into ring * resonance stabilisation not as great as in carboxylate ion * -ve charge dispersed, phenoxide ion stabilised carbo acid: * has 2 equivalent resonance structures ( -O and =O) * -ve charge delocalised over 2 highly electronegative O atoms * -ve charged more effectively dispersed halogen carbo acid: * electronegative halogen exert (greater) e- withdrawing effect, dispersing -ve charge on O * carboxylate ion most stabilised conguate base more stable, acid more acidic

dependent on: * e- deficiency of C bonded to halogen * steric factors that hinder attack by nucleophile COCl: * carbonyl carbon highly e- deficient as bonded to 2 e-ve atoms (O&Cl) * carbon is sp2 hybridised (triginal planar), less steric hindrance * most susceptible to nucleophilic attack CH2Cl: * carbonyl carbon less e- deficient as only bonded to 1 e-ve atom (Cl) * sp3 hybridised (tetrahedral) more steric hindrace * less susceptible to N attack B-Cl: * p orbital of Cl overlap with pi e- cloud of B ring, lone pair e- from p orbital delocalise into ring * C-Cl bond partial double bond character * benzene ring also repel attcking nucleophile attack by :OH nucleophile to convert acyl chloride to carboxylic acid

Alkane: * non polar, least e needed to overcome weak id-id, lowest mp COOH and Amine: * both polar, have stronger id-id, pd-pd and H2 bond * O more e-ve than N, larger dipole moment, O-H bond more polar than N-H bond, H2 bond in COOH stronger * COOH higher bp than Amine Amino Acid: * structure: zwitterions held tgt by strong ionic bonds * largest amt of e to overcome, highest bp