Alcohol phenol and Ether Flashcards
Classification of alcohols?
On the basis of no of OH groups and hybridization
Bond angle b/w CH in alcohols phenols and ether?
Order R-OH<AR-OH<ROR’
ROH 108°
AR-OH 109°
ROR’ 111°
Methods of prep of ROH? (Total7)
(1)
RX on treatment with aq.NaOH/KOH by nucleophilic substitution gives ROH
FROM ALKENES
(2) {By symmetric alkenes}
C=C +H2O (by markonikov) gives ROH
(3) Alkenes hydroboration oxidation {by asymmetric alkenes}
C-C=C +H2O2 (by anti markonikov) in presence of BH3/THF gives ROH
(4) Oxymercuration and demercuration
C-C=C + Hg(OAc)2 in presence of H2SO4/NaBH4{reducing agents} gives ROH
FROM CARBONYL COMPOUNDS
(5) Reduction
in aldehyde and ketones adding Ni/Pd/Pt in presence of NaBH4/LiAlH4 gives ROH
(6) Reduction
In ether and carboxylics adding Dil.H2SO4/NaBH4 gives ROH
FROM GRIGNARD
(7)
in aldehydes and ketones adding RMgX followed by hydrolysis gives ROH
Prep methods for phenols?(Total 6)
(1) From haloarenes
Chlorobenzene reacts with NaOH at (623k & 300atm) forming intermediate followed by rxn with HCl gives phenol.
(2) From benzene sulphonic acid
To benzene add olleum (conc.h2so4) forming sulphonic acid followed by rxn with NaOH then HCl to give phenol.
(3) From diazoinium salt
Form diazonium salt from aniline then to BDC salt add warm H2O which gives phenol+{N2&HCl gases are liberated}
Important name rxn ⤵️
(4) From cumene {aka benzene isopropyl}
On oxidation (O2) of cumene intermediate (cumene hydroperoxide) is formed which is then hydrolyzed to obtain phenol and acetone.
{Only prep of phenol which gives generous amount of acetone}
(5) By simply strong oxidation (V2O5/KMnO4) of benzene we get phenol
(6) On reacting salicylic acid with NaOH + CaO phenol is obtained
Physical properties of alcohols? ( Bp, solubility)
(1)B.P directly proportional to molecular mass {due to increased van der waal forces }
and inversely proportional to branching{due to decreased in van der waal forces with dec in surface area}
{To remember}BP order⤵️
RCOOH > ROH> RCHO > RCOR’ > ROR’
reasons:⤵️
In RCOOH dimerisation and H bonding
In ROH H bonding
In RCHO and RCOR’ dipole dipole interaction
In ROR’ induced dipole
(2) Solubility inversely proportional to R group
As R groups are hydrophobic ➡️incr. R group decr.solubility
Chemical properties of alcohols?
(1) Reactions involving cleavage of O-H bond
a) Rxn with metals : ROH and AR-OH react with active metals Na,F,Al to give phenoxide
b) Acidity of ROH : acidity directly proportional to-I effect and inversely proportional to+I effect
more R group more +I effect and less acidity
*ROH are weaker than H2O because in ROH presence of R group shows +I effect and no such effect is observed in H2O
c) Reactions:⤵️
> Esterification : when ROH reacts with RCOOH it gives RCOOR’
> All haloalkanes rxn : ROH reacts with (lucas reagent)
(PCl3) (PCl5) (SOCl2)
> Dehydration : ROH rxn with conc.H2SO4 at 443k gives alkene(learn mechanism)
*At 413k ether is obtained
> Oxidation : ROH reacts with strong oxidising agent (KMnO4/K2Cr2O7) to give RCOOH
> 1°ROH gives RCHO and 2° gives RCOR’
Reason for bond angles of ROH AR-OH ROR’?
In ROH due to repulsion b/w unshared pair of lone paired electrons of O
In AR-OH (i) partial double character on accnt of conjugation of e- of O with ring
(ii) sp2 hybridised state of C to which O is attached
In ROR’ repulsion b/w bulky R groups
MECHANISM of Prepration of ROH from alkenes
Book :) (pg 199)
MECHANISM of hydroboration oxidation
Book :)(pg 200)
Prep of R-OH using LiAlH4 (reduction) is expensive then which method is preferred insted?
RCOOH + ROH (esterification) in pres mce of acidic medium (H+) gives RCOOR’ which is further reduced using H2 to give R-CH2-OH+ R’OH
