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alcohols Flashcards

1
Q

why is the c-o-h bonde angle less in alcohola as compared to tetrahedral angle (109.28)

A

due to repusionbtwn unshaired e- pairs of O2

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2
Q

why is bond lenght in phenol slightly less than in methanol

A

This is due to partial double bond character on account of the conjugation of unshared electron pair of oxygen with the aromatic ring and a sp2 hybridised state of carbon to which oxygen is attached.

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3
Q

in ethers bond angle is slightly more than tetrahedral angle

A

repulsive interaction of bulky R grp

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4
Q

mechanism of acid catalysed hydration

marks rule

A
  1. protonation of C=C to form C+ by electrophilic attacvk of H2O
  2. NU:- attack of H2O on C+
  3. deprotonation to form alcohol
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5
Q

addition product of renx of diborane(H-BH2)2 with C=C

anti mark

A

trialkyl borane

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6
Q

COMErcial preparation of alchol from RCOOH

LiAlH4 is expensive

A
  1. add lil R’OH / H+
  2. RCOOR’
  3. CATALYTIC HYDROGENATION
  4. RCH2OH + R’OH
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7
Q

carbolic avid

A

phenol

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8
Q

comercial preparation of phenol

A

cumene
isopropyl benzene

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9
Q

benzene sulphonic acid is prepared by

A

benxene + oleum

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10
Q

nitrous acid used in preparation of diazonium salt at 273- 273K is

ride - warm water

A

NaNO2 + HCl

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11
Q

by product o phenol prepared by cumene is

A

acetone

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12
Q

oxidation of cumene in presence of air

A

cumene hydroperoxide

after that H+/ H20-> phenol + acetone

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13
Q

what happens when elimination competes over subtitution in dehydration of alcohols

A

alkenes are formed

ROH + h2so4 in 443K

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14
Q

dehydration of alcohol to form ether at 413K in prsene of protic acid like h2so4 is which mechanism

A

sn2

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15
Q
A
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16
Q

how are phenols converted to ethers

A

williamson

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17
Q

in BP no. of C atom increases what happens to van der waals force

A

increases

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18
Q

why does with increase in branching BP decrease

A

vander waals force decrease

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19
Q

high BP of R-OH is due to

ROH> ROR’ > RR

A

intermolecular H bonding

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20
Q

why does with increase in alkyl part solubility decreases

A

due to increase in HYDROPHOBIC CHARACTER of alkyl grp

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21
Q

which bond is broken when alco🪓hol is nuclephile

A

oh

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22
Q

which bond is broken when alc🪓ohol is electrophile

A

co

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23
Q

how is polarity related to acid strenght

A

polarity decreases acid strenght decreases

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24
Q

test to show phenols more acidic than ROH

A

Ar -O -H +NaOH-> Ar-ONa +H2O

sodium phenoxide +water

25
Q

how do u explain the acidic strength of ROH
1o>2o>30

A

as ERG (-ch3, c2h5) increase e- density on O this decrease polarity of O- H bond
this decreases acid strenght

26
Q

show water is more acidic than alcohol

A

R::O:- + H-:O:-H -> ROH + :::OH

base + acid -> conjugate acid + conjugate base

27
Q

why does alcohol act as bronsted bases

A

Due to presence of lone pair of electrons on oxygen atom, alcohols accept a proton which makes them Bronsted base

28
Q

Alcohols act as Bronsted acid and Bronsted base both Explain

A

Due to presence of lone pair of electrons on oxygen atom, alcohols accept a proton which makes them Bronsted base and due to acidic hydogen they donate the proton to strong base which makes them Bronsted acid.

29
Q

why does polarity of O-H in phenol increases

A

due to high electronegativity of sp2 C to which O-H is attached e- density decrease and polarity increases

30
Q

why is thepresence of EWG enhance the acidic strength more pronanciicng at o and p posts

A

due to effective delocatisation of -ve charge in phenoxide ion when substituent is at o and p post

31
Q

what does reactind RCOOH, RCOCl, (RCO)2with ROH gives

A

ESTER
RCOOR’

32
Q

THE rnc with RCOOH and (RCO)2 is carried out in the presence of small amount of conc H2SO4but RCOCl is carried out in pyridine whyy

A

to neutralise HCL and shift EQUILIBRIUM to RHS

33
Q

ACETYLATION

A

THE INTRO OF ACETYL GROP CH3CL in alcohols or phenols

34
Q

acetylation of salicylic acid gives

A

ASPIRIN
(acetyl salicylic acid)

35
Q

how do u differentiate 1o 2o and 3o alcohols

A

by lucas test
(HCl +ZnCl2)
3o- turbidity immediately
2o - turbidity after few mins
1o - X turbidity at rooom temp

36
Q

which bond is cleaved when phenol react with zn

37
Q

by product of R-OH reacted with phosphorus trihalide

38
Q

Ethanol + heat at 443K + con h2so4gives

A

ethene
undergoes DEHYDRATION

39
Q

PROPAN-2-Ol with 85% h3po4 at 440K

A

ch3-ch=ch2 + h2o

40
Q

2 methylpropan-2-ol react with 20% h3po4 at 358K

A

2 methylpropene

41
Q

mechanism of DEHYDRATION

3o>2o>1o

A
  1. formation of protonated alchol
  2. formation of C+ (slowes and rate deter)
  3. formation of ethene by elimination of proton

to drive hte equi to the right ethene is removed

42
Q

which all bond are cleaved in alcohol to for C=O durind oxin
and is called

A

C-H and O-H

dehydrogenation

43
Q

under high temp and strong oxi agents tertiary alcohols cleave various C-C bond to forms >?

A

mixture of RCOOH containing lesser no. of C atoms

44
Q

what happens when vapors of
1. 1o
2. 2o
3. 3o

alcohols are passed over heated cu at 573K

A
  1. RCHO
  2. RC=OR’
  3. dehydration: alkene is formed
45
Q

how OH group activates the incoming electrophile to o and p posts

A

OH group exerts +R effect on the benzene ring. So, electron density in the ring increases particularly at the ortho and para positions

46
Q

phenol + dil nitric acid gives

298K

A

phenol + dil.HNO3-> o and p- nitro phenol

47
Q

phenol + con nitric acid gives

A

phenol + dil.HNO3-> 2,4,6-Trinitro phenol

aka picric acid

48
Q

how do u separate o and p- nitro phenol

A

separated by steam distillation
* *o *- nitroph is steam volatiledue to intramolecular h bonding
* p - nitroph is less volatile due to intermolecular h bonding which causes association of molecules

49
Q

phenol + halogen in chcl3/CS2 ->

A

monohalophenols

50
Q

why is halogenation of phenols occur in the absence of lewis acid feBr3

A

in usual halogentaion of benzene the lewis acid polarises the halogen molecule

due to high activating effect oF OH grp polarisation of bromine occurs even wothout lewis acis FeBr3

51
Q

when ph is reacted with bromine water

A

2,4,6-tribromoph + 3HBr
white ppt

52
Q

kolbe’s rnx

A

ph+ NaOH-> ph-ONa+ -(i)CO2/(ii)H+->
SALICYLIC ACID

phenoxide is more reactive so it undergoes ESR wih CO2. a weak electrophile

53
Q

REIMER - TEIMANN

A

ph+ chcl3 +aq NAOH-> intermediate- NAOH->phONa+&CHO -H+->
SALICYLALDEHYDE

54
Q

IN PRESENCE OF AIR, phenols are oxidised to dark coloured mixture :

55
Q

🌴👻

colourlss and bp-337K

A

methanol
ch3oh

catalytic hydrogention with zno+cr203

200-300atm and 573 to 673K

56
Q

what is added to ethanol(bp- 351K) to denature its colour and smell

A

colour- copper sulphate
smell - pyridine

57
Q

which alkyl grpsin 1o and 2o are attacked by iodine(nucleophile)by SN2 mechanism

A

the lower onch3I

57
Q

alkyl aryl ethers are cleaved at the alkyl O2 bond??

A

due to stability of aryl O2 bond

58
Q

or GROUP IS ACTIVATING AN D— directing

Chemistry (9 decks)

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