Hydroxy Compounds Flashcards by Happy Cookie

[Hydroxy compounds] aliphatic vs aromative/ alocohol vs phenol

Alcohol is aliphatic
-OH to sp3 hybridised C

Phenol is aromatic
sp2 hybridised C in benzene ring

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[Hydroxy compounds] Physical properties of Alcohol

boiling/melting points
Solubility in polar/non-polar solvents
Type of molecular attraction

bp higher than alkanes of similar Mr
soluble in H2O and organic
Solubility decrease when C increase
idid, H-bonds

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[Hydroxy compounds] Bp of alcohols

Alcohol > alkane (for comparable Mr)
more energy to over stronger H bonds between alcohol molecules than weaker idid between alkane

Length of alkyl chain
increase size, increase e, more polarisable e cloud
Branching
more branching, more spherical, less SA, less extensive idid

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[Hydroxy compounds] Solubility of alcohol in H2O

alcohol > alkanes
more soluble in H2O
-OH present, form H bond

Decrease solubility when C increase
miscible with organic solvents

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[Hydroxy compounds] Solubility of alcohols in organic (non polar) and polar solvents

Soluble in both due to
polar -OH
non polar hydrocarbon chain

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[Hydroxy compounds] alkene to alcohol

Electrophilic addition

LABORATORY
conc H2SO4, cold
H2O, heat
INDUSTRIAL
conc H3PO4 catalyst
Steam
heat

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[Hydroxy compounds] Halogenoalkane to alcohols

Nucleophilic substitution
Aqueous NaOH/KOH
heat

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[Hydroxy compounds] Aldehyde/Ketone to alcohol

Aldehyde (-CHO) to pri 1 alcohol
Ketone (-CO) to sec 2 alcohol

3 possible reagents

LiAlH4 in dry ether, rt
NaBH4 in ethanol, rt
H2, Ni/Pd/Pt catalyst, rt

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[Hydroxy compounds] Carboxylic acid to alcohol

Reduction
LiAlH4 in dry ether, rt

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[Hydroxy compounds] Sites of reactivity

3 sites of reactivity

electron deficient C
partial pos
susceptible to nucleophilic attack
R-OH as electrophile
high electron density O partial neg
R-OH as nucleophile
O-H polarised bond
RO-H as B-L acid

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[Hydroxy compounds] Combustion of alcohol

Pale blue flame
CO2 and H2O

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[Hydroxy compounds] Alcohol to alkene

Dehydration/ Elimination reaction
excess conc H2SO4, heat
or Al2O3 catalst, heat
or conc H3PO4 catalyst, heat

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[Hydroxy compounds] Alcohol to halogenoalkane R-X

nucleophilic sub
UNCONFIRMED LIST VERY MESSY WILL UPDATE BUT

conc HCl, ZnCl2 catalyst, heat
R-X and H2O

anyhydrous PX3, heat
R-X and H3PO3

anhydrous PCl5 rt
R-Cl abd POCl3 and HCl (g)
can sep products

anhydrous SOCl2, heat
R-Cl and SO2(g) and HCl(g)
cannot separate

Observation:
White fumes of HCl for PCl5 and SOCl2

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[Hydroxy compounds] Oxidation of pri vs sec vs tert alochols

*PRI:** aldehyde(-CHO)/carbo acid(-COOH) +H2O
*SEC:** ketone (-CO) +H2O
*TERT:** resistant to [O], absence of alpha H

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[Hydroxy compounds] Secondary alcohol to ketone

Oxidation
Acidified KMnO4/K2Cr2O7, heat
Observations: purple to c-less/orange to green

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[Hydroxy compounds] Primary alcohol to aldehyde/carbo acid

Oxidation
1. CARBO ACID AS PRODUCT
Acidified KMnO4/K2Cr2O7, heat
Observations: purple to c-less/orange to green

ALDEHYDE AS PRODUCT
Acidified K2Cr2O7, immediate distil
KMnO4 is too strong
Observation: orange to green

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[Hydroxy compounds] Test for alcohol

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Iodoform
Brown I2 decolourise, pale yellow ppt CHI3 formed
eqn 6 4 1 5 5

[Hydroxy compounds] Step down reaction of alcohol

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Iodoform
Brown I2 decolourise, pale yellow ppt CHI3 formed
eqn 6 4 1 5 5

[Hydroxy compounds] alcohol to ester

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Nucleophilic acyl sub
Add -COOH and conc H2SO4 catalyst, heat under reflux
product ester and H2O

or add acyl chloride at rt
product ester and HCl
Preferred becauase milder conditions, go to completion, HCl gas can be removed

[Hydroxy compounds] reaction mechanisms involved in nucleophilic acyl sub (alcohol + ? → ester)

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Addition of nucleophile (alcohol)
Elimination of H and the other one

[Hydroxy compounds] Physical properties of phenol

boiling/melting points
Solubility in polar/non-polar solvents
Type of molecular attraction

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bp/mp phenol>alkane
bp depends on extent of intramolecular H bond
promity of groups like NO2 or OH

sparingly soluble in H2O
weakly acidic

[Hydroxy compounds] Structure of phenols

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Oxygen has 2 lone pair e
O has one sp2 hybridised
the other unhybridised 2p orbital side on overlap with pi e cloud of benzene
and delocalised in bezene ring

[Hydroxy compounds] Delocalisation on 2p unhybridised lone pair of e affects

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reactivity of -OH
reactivity of benzene ring

[Hydroxy compounds] Sites of reactivity for phenols

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OH group:
1. Delocalised lone pair e on O
weak nucleophile
2. Polarised O-H bond
dispersal of neg charge
stabilised conjugate base

Benzene ring:
1. delocalised lone pair into benzene ring
partial double bond character
poor electrophile
2. delocalied lone pair into ring
activated electrophilic sub
benzene ring as nucleophile

**[Hydroxy compounds]** Combustion of phenol

very smokey orange flame combustion is hardly complete need very high O;phenol proportion

**[Hydroxy compounds]** Phenol to ester

Add acyl chloride, phenol in NaOH rt get ester and HCl very slow UNLIKE NORMAL ALCOHOL carbo acid and phenol will not react

**[Hydroxy compounds]** for nucleophilic acyl sub to convert phenol to ester why must the phenol be in NaOH

Phenol and NaOH gives acid base reaction convert phenol to phenoxide (neg charge) stronger nucleophile

**[Hydroxy compounds]** why do phenols not undergo nucleo sub like alchols

unhybridised 2p orbital lone pair e side on overlap with pi e cloud lone pair e delocalised into benzene ring partial double bond character strengthening CO bond benzene ring also repels nucleophile because electron rich

**[Hydroxy compounds]** Why can phenols undergo electrophilic sub

can electro sub but milder conditions than benzene/methylbenzene 2p orbital unhybridised in O lone pair of e side on overlap with pi e cloud delocalised into ring benzene ring more e rich more susceptible to electrophilic sub

**[Hydroxy compounds]** Positions of addition/sub in phenol

2,4-directing because strongly ring activating 2,4,6

**[Hydroxy compounds]** Acidity factors

relative stability of conjugate base H-A ⇌ H+ + A- more stable conjugate base A- equilibrium pos right more H+ because greater dissociation stronger acid HA e donating groups intensify neg charge destabilise conjugate base e withdrawing groups disperse neg charge stabilise conjugate base

**[Hydroxy compounds]** Ranking acidity of H20 Ethanol and Phenol

Ethanol \< H2O \< Phenol ethanol CH3CH2 intensifies neg charge **destabilises ethoxide ion** relative to hydroxide phenol 2p unhybridised lone pair e side on overlap with pi e cloud delocalised into ring disperse neg charge **stabilise phenoxide ion** resonance stabilised

**[Hydroxy compounds]** Alcohols and phenols with metals (Na)

Form alkoxide/phenoxide and half mole of H2 cleavage of O-H bonds Redox less vigourous reaction than water because alcohols are weaker acids

**[Hydroxy compounds]** Alcohols and phenols with bases (NaOH)

Form alkoxide/phenoxide and half mole of H2 only phenols and carbo acid alcohols are weaker acids cannot undergo a-b reaction

**[Hydroxy compounds]** Alcohols and phenols with Carbonate (CO3 2-)

acid-carbonate reaction alcohols no reaction phenols and carbo acid can technically react but only carbo will go to completion (CO2 produced) phenol not acidic enough GOOD TEST FOR COOH because CO2 produced

**[Hydroxy compounds]** test for hydroxy compunds (all including phenols and carbo)

add Na H2 gas should extinguish lighted splint with a pop sound

**[Hydroxy compounds]** test for carboxyl COOH group

Add sodium carbonate CO2 effervescence white ppt in limewater

**[Hydroxy compounds]** Test to identify aliphatic alochols

1. Nu sub 2. Acid metal reaction 3. oxidation 4. iodoform

**[Hydroxy compounds]** identify aliphatic alcohol using nu sub

anhydrous PCl5, rt OR anhydrous SOCl2, heat HCl white fumes

**[Hydroxy compounds]** Identify aliphatic alcohol by oxidation

only works for pri and sec alcohol because tertiary has lack of alpha carbon ``` Add acidified (H2SO4) KMnO4/K2Cr2O7 positive: purple→colourless/orange→green neg/tertiary: remain purple/orange ```

**[Hydroxy compounds]** Iodoform test

only for the C H OH CH3 group NaOH and I2 (aq), heat decolourise brown I2 pale yellow ppt CHI3

**[Hydroxy compounds]** Test for phenol FeCl3

Add neutral FeCl3 (aq) at rt violet colour for positive test from complex ion

Hydroxy Compounds Flashcards

(42 cards)