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Classification of alcohols
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Classification of Alcohols
i). Alcohols contain the functional group -OH (hydroxyl group) ii) From a given alkane one, two, three hydrogen atoms may be replaced by one, two, three hydroxyl groups, to give monohydric, dihydric, trihydric alcohols respectively iii) The general name polyhydric alcohol indicates that the alcohols contains more than one -OH group.
Methyl alcohol (CH3OH) ,Ethyl alcohol (C2H5OH) , isopropyl
alcohol (CH3)2CHOH, Tertiary butyl alcohol (CH3)3COH etc.are monohydric
alcohols. (CH2OH−CH2OH) is dihydric, glycerol (CH2OH−CHOH−CH2OH) is trihydric,
sorbitol or mannitol {(CH2OH)−(CHOH)4−CH2OH} is hexahydric.
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MONOHYDRIC ALCOHOLS(R-OH)
The general formula of the homologous series of
monohydroxy alkanes isCnH2n+1OH or R−OH where R is alkyl group.
i). If −OH group is bound to a primary carbon atom it is called a primary
alcohol.
Ex: Methyl alcohol (H−CH2OH) ;
ethyl alcohol (CH3−CH2−OH);
n-Propyl alcohol (CH3−CH2−CH2−OH) ;
isobutyl alcohols etc. are primary alcohols.
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TERTIARY ALCOHOLS(R-OH)
iii) Tertiary alcohol contain-OH group bound to a tertiary carbon atom.
Example:Tertiary butyl alcohol:
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COMPOUNDS CONTAINING Csp3−OH
In this class of alcohols, the -OH group is attached to
an sp3 hybridised carbon atom of an alkyl group. they are further classified as
follows:
primary (H−CH2OH) Secondary
Tertiary
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ALLYLIC ALCOHOLS
In these alcohols, the - OH group is attached to a sp3 hybridised carbon next to the carbon carbon double bond, that is to an allylic carbon.
Primary CH2=CH−CH2−OH
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BENZYLIC ALCOHOLS
In these alcohols, the - OH group is
attached to a sp3 -hybridised carbon atom next to an aromatic ring. Allylic and
benzylic alcohols may be primary, secondary or tertiary.
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COMPOUNDS CONTAINING Csp3−OH bond
These alcohols contain -OH group bonded to a carbon - carbon double bond i.e., to a vinylic carbon or to an aryl carbon. These alcohols are also known as vinylic alcohols.
Vinylic alcohol: CH2=CH−OH
IUPAC Nomenclature
1
IUPAC NOMENCLATURE OF ALCOHOLS
i). The substitutive names of alcohols are given by identifying the longest continuous carbon chain containing the hydroxyl group and replacing the ending letter of the name of the corresponding alkane e by ol. ii). The carbon atoms in the identified longest chain are numbered such that the carbon carrying the -OH group gets the lowest possible number.
Example:Ethanol CH3−CH2−OH
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NAMING OF PHENOLS
Molecule Common name Phenol IUPAC name
Phenol
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NAMING OF PHENOLS
Molecule Common name O-cresol IUPAC name 2-methyl phenol
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NAMING OF PHENOLS
Molecule Common name
m-cresol IUPAC name 3-methyl phenol
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NAMING OF PHENOLS
Molecule Common name Catechol IUPAC name Benzene-1,2-diol
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NAMING OF PHENOLS
Molecule Common name Resorcinol IUPAC name Benzene-1,3-diol
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NAMING OF PHENOLS
Molecule Common name Hydroquinone (or)quinol IUPAC name Benzene-1,4-diol
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NAMING OF PHENOLS
Molecule Common name 2,6-Xylenol IUPAC name 2,6-dimethyl phenol
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ETHER NOMENCLATURE
Ethers are the carbon compounds containing Oxygen atom linked to two
alkyl groups. The general formula of ethers is R−O−R or (CnH2n+1)2O or CnH2n+2O.
The radico -functional names of ethers are derived by listing the two alkyl groups in an alphabetical order as separate words and then adding the word ether at the end.
Ethers are considered to be dialkyl derivatives of water. They are named in two ways namely a) common system and b) IUPAC
System In common system, ethers are named after alkyl groups attached to oxygen
atom. For simple ethers , the common name is di alkyl ether.For mixed ethers, the
common name is alkyl, alkyl ether.Ethers are named first in the alphabetical order followed by the word ether in common system.
In IUPAC system, Ethers are named as alkoxy alkanes. The smaller alkyl group along with Oxygen atom is taken as alkoxy part while the larger alkyl group as alkane part.
Formula Common name IUPAC name
CH3OCH3 dimethyl ether methoxy methane
CH3OC2H5 ethylmethylether methoxy ethane
C2H5OC2H5 diethyl ether ethoxy ethane
CH3OC3H7 methyl n-propyl ether methoxy propane
C2H5OCH(CH3)2 ethyl isopropyl ether 2-ethoxy propane
C6H5OCH3 Anisole Methoxy benzene
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Naming of acids are the derivatives of acetic acid
(i) Except formic acid i.e., methanoic acid (H-COOH) remaining acids are
named as acetic acid.
Acid IUPAC Name Name of derivatives of acetic acid
1)CH3−CH2−COOH Propanic acid methyl acetic acid
2)CH3−CH2−CH2−COOH Butanoic acid ethyl acetic acid
3)(CH3)3C−COOH 2,2-dimethyl propanic
acid. Trimethyl acetic acid
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NAMING OF AROMATIC ACIDS-IUPAC NOMENCLATURE
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IUPAC NOMENCLATURE OF CARBOXYLIC ACIDS
IUPAC system of saturated aliphatic mono carboxylic acids contain a) Root word is Alk b) Primary suffix - ane c) Secondary suffix - oic acid Hence alkanoic acid is the IUPAC name of saturated aliphatic mono carboxylic acids Carboxylic acids are named as
Alkanoic acids.
Formula source common Name IUPAC Name
HCOOH 'Red ant Formic acid Methanoic acid
CH3COOH Vinegar Acetis acid Ethanoic acid
C2H5COOH Protonpion propionic acid propanoic acid
C3H7COOH Butter Butyric acid Butanoic acid
C4H9COOH Valerian plant Valeric acid Pentanoic acid
Formula Common
Name IUPAC Name
(CH3)2CHOOH Isobutyric
acid 2-methyl propanoic acid
HOOC−COOH Oxalic acid Ethane-1,2-dioic acid
HOOC−(CH2)2−COOH Succinic acid Propane-1,3-dioic acid
HOOC−(CH2)3−COOH Glutaric acid Butane-1,4-dioic acid
HOOC−(CH2)4−COOH Adipic acid Hexane-1,5-dioic acid
HOOC−CH2CH(COOH)−CH2COOH - Propane-1,2,3-tricarboxylic acid
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NOMENCLATURE : ALDEHYDES & CARBOXYLIC ACIDS
Common System : Aldehydes names are derived from corresponding Carboxylic acids to which they are oxidised. The suffix ic acid is replaced by aldehyde. In IUPAC system aldehydes are named as Alkanals and Carboxylic
acids are named as Alkanoic acid. Common name IUPAC name HCHO Formaldehyde Methanal
CH3CHO Acetaldehyde Ethanal
CH3CH2CHO Propionaldehyde Propanal
HCHO−→OHCOOH
Formaldehyde Formicacid
CH3CHO−→OCH3COOH
Acetaldehyde Aceticacid
CH3CH2CHO−→OCH3CH2COOH
Propionaldehyde Propionicacid (CH3)2CHCHO−→O(CH3)2CHCOOH
2-methyl propanal 2-methyl propanoic acid
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NOMENCLATURE : KETONES
In case of simple ketones, they are named as - dialkyl ketones. In case of mixed ketones, - names of Alkyl groups are prefixed in alphabetical order. In IUPAC system, Ketones are named as Alkanones.
CH3COCH3 Common name- Dimethyl Ketone. IUPAC name-Propanone
CH3COCH2CH3 Common name- Ethyl Methyl Ketone. IUPAC name-
Butanone-2
Properties of Alcohols
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Structure and Bond angle -Alcohols
Structure of OH functional group- In alcohols, the oxygen of the -OH group is attached to carbon by a
sigma (σ ) bond formed by the overlap of a sp3 hybridised orbital of carbon
with a sp3 hybridised orbital of oxygen. The bond angle in alcohols is slightly
less than the tetrahedral angle (109∘28′) . It is due to the repulsion between
the unshared electron pairs of oxygen.
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METHODS OF PREPARATION OF ETHYL ALCOHOL
i) Ethyl alcohol is called grain alcohol as it is obtained from starchy grains. ii) Ethyl alcohol is a constituent of wines and it is called spirit of wine.
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PREPARATION METHODS OF ETHYL ALCOHOL
From ethyl halide-Nucleophilic substitution reaction Ethyl halide on hydrolysis with aqueous sodium hydroxide or potassium hydroxide or silver hydroxide suspended in boiling water forms ethyl alcohol.
CH3CH2X+NaOH(aq)→CH3CH2OH+NaX
Where X=Cl,Br,I
CH3CH2X+AgOH→ΔCH3CH2OH+Agx
Saponification reaction Ethyl alcohol is formed by the hydrolysis of ethyl acetate (an ester) with
aqueous alkali.CH3COOC2H5+KOH(aq)→CH3COOK+C2H5OH or
RCOOH−→−−R′OHH+RCOOR′−→−−−catalystH2RCH2OH+R′OH
Reduction or Hydrogenation of Aldehydes or ketones i) Acetaldehyde forms ethyl alcohol when it is reduced with a suitable reducing
agent like lithium aluminium hydride (LiAlH4) in ether.
ii) Acetaldehyde on catalytic hydrogenation also forms ethyl alcohol. iii) The catalyst may be nickel, platinum, palladium etc. CH3CHO−→−−−−−−−−−−−−−orH2/Ni/pd/ptLiA/H4/etherorNaBH4CH3CH2OH
Reduction of carboxylic acids-
Carboxylic acids are reduced to primary alcohols with LiAlH4, a strong
reducing agent.
RCOOH−→−−−−ii)H2Oi)LiAlH4RCH2OH
From ethylene- Addition reaction On large scale) ethylene is formed in large quantities during CRACKING of petroleum.
Ethylene is passed into 98% conc. H2SO4 at 75−80∘C under pressure to get
ethyl hydrogen sulphate (C2H5H5O4).
This mixture is diluted with water and warmed so that hydrolysis takes place to get alcohol.H2C=CH2+H2SO4→C2H5HSO4 C2H5HSO4+H2O→C2H5OH+H2SO4
Fermentation of molasses or starch
C12H22O11+H2O−→−−−−yeastinvertaseC6H12O6(glucose)+C6H12O6(fructose)
C6H12O6−→−−−−−−−−−−−−yeastglucoseorfructosezymase2C2H5OH+2CO2
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NUCLEOPHILIC ADDITION MECHANISM-Step1
i) Protonation of alkenes to form carbocation by
electrophilic attack of H3O⨁.
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NUCLEOPHILIC ADDITION MECHANISM
Nucleophilic attack of water on carbocation
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NUCLEOPHILIC ADDITION MECHANISM
Deprotonation to form alcohol
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HYDROBORATION - OXIDATION METHOD
Alkenes undergo addition reaction with diborane. The addition compounds on hydrolysis.6(CH2=CH2)+B2H6→2(CH3CH2)B
(CH3CH2)3B+3H2O→OH−3CH3CH2OH+H3BO3
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REDUCTION OF ALDEHYDES, KETONES AND CARBOXYLIC ACIDS
Sodium borohydride (NaBH4) is the convenient reagent to carry out the
reduction of aldehydes or ketones into alcohol.
RCHO−→−−−−−−−−−2H3O+1)NaBH4inalcoholRCH2OH.
LiAlH4 is better reducing agent for the conversion of carbonyl compounds,
carboxylic acids and their derivatives into alcohols.
R−COOH+4(H)→LiAlH4RCH2OH+H2O
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METHANOL PREPARATION
CO+2H2−→−−−−−−−−−−−−200−300atm,573−673kZnO−Cr2O3CH3OH
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PHYSICAL PROPERTIES OF ETHYL ALCOHOL
Ethyl alcohol is a colourless pleasant smelling liquid and has burning taste. It is inflammable and burns with a blue flame. Its boiling point is higher than corresponding ether,alkyl halide and
alkanes due to strong intermolecular hydrogen bonding.
Compound MW/b.p (k)
CH3CH2OH 46/351
CH3OCH3 46/248
CH3CH2CH3 44/231
Its B.P is 78.1∘C . Its Higher b.p is due to presence of inter molecular
hydrogen bonding. As the number of carbon atoms increase, the boiling point of alcohols increase. This is due to increase in vanderwaals forces of attractions.
Among isomeric alcohol, b.p order is primary > secondary > tertiary Reason: Primary alcohol have more inter molecular force of attraction than in secondary alcohol, which has more than in tertiary alcohol.
It is soluble in water in all proportions due to H-bonding and contraction in volume occurs due to evolution of heat.
A mixture of 96.5% ethyl alcohol and 4.4% water is called constant boiling point mixture. It is also known as Azeotropic mixture it can be dried by using anhydrous CaO and finally with Ca is used to get 100% alcohol or absolute alcohol.
It is soluble in organic solvents such as ether, benzene etc.. in all
proportions.
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Chemical properties of Alcohol
Ethanol (primary alcohol) under goes reactions involving polar bonds
(O−H &C−Obond)
Alcohols react both as nucleophiles (due to O−H bond cleavage) and
electrophiles (due to C−O bond cleavage).
Alcohols can show two types of reactions due to cleavage of O−Hbond or
cleavage of C−O bond.
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REACTIONS INCVOLVING CLEAVAGE OF O-H BOND
Reaction with active metals
C2H5OH→Na(or)KCH3−CH2−ONa+12H2
This shows acidic nature of alcohol. Ethyl alcohol is neutral towards litmus paper, cannot react with any base but liberates hydrogen gas with sodium metal supporting acidic nature of ethyl alcohol. Acidic nature of alcohol is less than water due to electron releasing alkyl group
base Acid Conjugate Conjugate Acid Base
6(CH3)3C−OH+2Al→2((CH3)3−C−O)3Al+3H2
Aluminium tert-butoxide. Conjugate basic strength are alkoxide ion is greater than hydroxide ion. As number of electron releasing alkyl groups increases, acidic strength of alcohols decreases. Among alcohols order of reactivity in the reacations due to O-H bond cleavage is CH3OH>1∘ROH>2∘ROH>3∘ROH
CH3OH>1∘ROH>2∘ROH>3∘ROH (acidic strength)
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REACTION WITH ACETIC ACID AND ITS DERIVATIVES
C2H5OH+CH3COOH−→−−−H2SO4H2OCH3COOC2H5+H2O Note : In the
above reaction H2SO4 acts as catalyst and dehydrating agent.(FISCHER
ESTERIFICATION) C2H5OH+CH3COCL→CH3COOC2H5+HCL
C2H5OH+(CH3CO)2O→CH3COOC2H5+H3CCOOHNote : In above
reactions, fruity odour ethyl acetate is obtained which is use to recognise
the OH functional group.
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REACTION OF ALCOHOL WITH GRIGNARD REAGENT
C2H5OH+RMgX→RH+C2H5OMgXalkane
C2H5OH+CH3Mgl→CH4+Mg(OC2H5)I
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REACTIONS INVOLVING CLEAVAGE OF C−OH BOND
Order of reactivity among alcohols for C-O cleavage is 3∘>2∘>1∘>CH3OH.
Action with Phosphorus halide-Nucleophilic substitution
3C2H5OH+PX3→3C2H5X+H3PO3Note : Basicity of H3PO3 is two, oxidation
state of phosphorous is +3
C2H5OH+PX5→C2H5X+POX3+HX (X = Cl, Br)
Action with nitric acid C2H5OH+HONO2→C2H5ONO2+H2O
(Ester of nitric acid) Action with thionyl chloride C2H5OH+SOCl2→pyride(C5H5N)C2H5Cl+SO2+HCl (HCl is absorbed by pyridine) Action with Hydrogen halide
C2H5OH+HX→CATALYST/ΔC2H5X+H2O
C2H5OH+HCl−→−−−−−−ConcH2SO4zncl2C2H5Cl+H2O
Note : Order of reactivity HI > HBr > HCl > HF
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ACTION WITH ALUMINA : (Dehydration)
C2H5OH→Al2O3/350∘CCH2=CH2+H2O
2C2H5OH→Al2O3/260∘CunderpressureC2H5OC2H5+H2O
Thus, the relative ease of dehydration of alcohols follows the following order. Tertiary > Secondary > Primary
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OXIDATION REACTIONS OF ALCOHOLS
Oxidation with KMnO4 and K2Cr2O7
C2H5OH−→−−−−−−−−−−−−−−−(O)H2SO4/KMnO4orK2Cr2O7CH3CHO→(O)CH3CO
OH
RCH2OH→CrO3RCHOCH3−CH=CH−CH2OH→PCCCH3−CH=CH−CHO
R−CH(OH)−R′→CrO3RCO−R′ Sec-alcohol Ketone
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DEHYDROGENATION: (Oxidation of alcohols)
C2H5OH→redhot′Cu′/300∘CCH3CHO+H2
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REACTIONS INVOLVING ALKYL GROUP AND ALCOHOL GROUP
IODOFORM REACTION C2H5OH+4I2+6KOH→CHI3+HCOOK+5KI+5H2O
Iodoform
Note : CHI3 is yellow crystalline solid.
Among primary alcohols, only ethyl alcohol and among secondary alcohols
only 2-alkanols can give iodoform reaction. Whereas, all tertiary alcohols can not give this reaction.
REDUCTION OF ALCOHOLS
C2H5OH+2HI−→−−HeatRedpC2H6+H2O+I2
REACTION WITH CHLORINE
C2H5OH+Cl2→CH3CHO→Cl2CCl3CHO
Chloral ACTION WITH BLEACHING POWDER
C2H5OH−→−−−−−−CaOCl2/OHrefluxedwithCHCl3+Ca(CH3COO)2
Chloroform Cal.Acetate
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MECHANISM OF DEHYDRATION OF ACOHOLS-STEP 1
It takes place in three steps : i) Protonation of alcohol as OH is poor leaving group, it is protonated to
form H2O+, a good leaving group.
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MECHANISM OF DEHYDRATION OF ALCOHOLS- STEP 2
ii) Formation of
carbonation. It is the slowest step or rate determining step.
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MECHANISM OF DEHYDRATION OF ALCOHOLS- Step 3
iii) Elimination of proton to get alkene. Since, the rate determining step is the formation of carbocation, the rate of dehydration is directly proportional to the formation of carbocation.
Since the stability of carbocation is 3∘>2∘>1∘ , the order of dehydration of
alcohols is
(CH3)3CHO>(CH3)CHOH>CH3−CH2OH
Dehydration of 1∘ alcohol requires 95% H2SO4 at H2SO417∘C,2∘alcohol
requires 75%
H2SO4 at 100∘, where as 3∘ alcohol requires 5% H2SO4 at 50∘C .
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MECHANISM OF DEHYDRATION OF ALCOHOLS
The dehydration of 1∘ alcohol goes by E2 mechnism, but that
of 2∘ and3∘ alcohols go by E1 mechanism. When more than one product is
formed, the major product is according to Zaitsevs rule. It states that hydrogen is removed from β carbon that is bonded to the least number of
hydrogen atoms.( β -elimination) Eg. Dehydration of 2-butanol predominantly
gives 2-butene.
CH3−CH2−CH2−CHOH−→−−−H2SO4ConcCH3−CH=CH−CH3+CH3−CH2−CH
=CH2
2-butene(major) 1-butene (minor)
Test for alcohols
1
Lucas test for Alcohols
1) Lucas test : The alcohol is treated with Lucas give turbidity
Reagent- Anhydrous ZnCl2 inc conc. HCl.
Primary alcohol No reaction (No turbidity) Secondary alcohol Reacts with in 5 minutes to 30 seconds to give turbidity Tertiary alcohol Reacts within 30 seconds to give turbidity
2
Victor Meyer Test for Alcohols
The alcohol is treated with red phosphorous and I2 and the product is treated
with AgNO2 and then with nitrous acid. (NaNO2+H2SO4) and finally made
alkaline. Primary alcohol: Red colouration is observed.
RCH2OH→I2redpRCH2I→AgNO2RCH2NO2→HNO2R−C4N2O2−OH(Nitricacid)→
alkaliredcolouration
Secondary alcohol Blue colouration is observed
R2CHOH→I2+RedpR2CHI→AgNO2R2CHNO2→HNO2R2−C3N2O3(pseudonitrol)→
alkalibluecolouration
Tertiary alcohol No colour is produce R3COH→I2+RedpR3CI→AgNO2R3CNO2→HNO2alkaliNoreaction
Phenols
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METHODS OF PREPARATION OF PHENOL
1) Phenol was first isolated from coaltar.
2
METHODS OF PREPARATION OF PHENOL
2) From haloarenes
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METHODS OF PREPARATION OF PHENOL
3) From diazonium salt :
4
METHODS OF PREPARATION OF PHENOL
4) From
benzene sulphonic acid :
5
METHODS OF PREPARATION OF PHENOL
5) From cumene : Phenol is manufactured from
cumene (isopropyl benzene) +CH3COCH3 cumene hydroperoxide
6
ACIDITY OF PHENOLS
The reactions of phenol with metals as well as NaOH indicate it is relatively more acidic than alcohols and also water. This is explained on the basis of the structure of phenol. The hydroxyl group in phenol is directly attached to Sp2 carbon of benzene ring.
The Sp2 carbon attached to O being more electronegative than Sp3 carbon of
alcohols, it decreases the electron density on oxygen. Because of this oxygen develops still more electron seeking character and releases proton by taking the shared pair of electrons with it.The acidic nature of phenol can also be explained .On the basis of resonance stabilization of phonoxide ion. Electron withdrawing groups of phenol increase the acidic nature. Electron releasing group of phenol decrease the acidity of phenols. Acidic strength increases with the decrease of the pKa values.The order of the
strength of phenols is as follows
7
PHYSICAL PROPERTIES OF PHENOLS
1) Phenol has higher boiling point than the arenes or haloarenes or ethers of same molecular weight. It is due to the formation of intermolecular hydrogen bond. 2) Phenols are relatively more soluble in water due to their ability to form hydrogen bonding with water. 3) As the hydrocarbon part increases in size and mass, the solubility
decreases.
8
CHEMICAL PROPERTIES OF PHENOLS
1) Acidic nature of phenol : Alcohols and phenols react with active metals like Na, K, Al etc to liberate hydrogen gas.
2ROH+2Na→2RONa+H2
C6H5OH+2Na→2C6H5ONa+H2
Phenols also react with aqueous NaOH solution to produce the salt sodium phenoxide and water. C6H5OH+NaOH→C6H5ONa+H2O
The acidic nature of alcohols is due to the polar nature of O-H group. Electron releasing groups like alkyl groups increase the electron density on oxygen and decrease the polarity of O-H bond. This decreases the acidic strength. The order of acidic strength is
H2O>RCH2OH>R2CHOH>R3COH
Even through the electron releasing groups like −CH3,−C2H5 etc decrease the
acidic strength of phenol, Phenol does not
liberate CO2with Na2CO3 or NaHCO3 because phenol is weaker acidic than
carbonic acid and carboxylic acids.
9
ESTERIFICATION OF PHENOL
Phenols react with carboxylic acids and their derivatives like acid chlorides and anhydrides to form esters. This reaction (benzoylation ) is called Schotten-Baumann reaction.
C6H5OH+RCOOH→C6H5−O−CO−R+H2O
C6H5OH+RCOCl−→−−−−pyridineC6H5−O−CO−R+HCl Salicylic acid on acetylation gives acetyl salicylic acid known as Aspirin. Electrophilic aromatic substitution reactions of phenol In phenol, -OH group is ring activating and ortho and para directing as these positions get more
electron density through resonance structures.
10
HALOGENATION OF PHENOLS
Here, no Lewis acids like FeBr3 are required because highly activating effect
of -OH group polarises bromine quickly. Phenol reacts with bromine water and gives 2,4,6- tribromo phenol (white precipitate)
11
C)REIMER-TIEMANN REACTION
Phenol when treated with chloroform in the presence of NaOH give salicylaldehyde. Mechanism :
i)CHCl3+OH−⇔H2O+CCl−3→:CCl2+CL−
Dichloro carbene (:CCl2) is the attacking electrophile in this reaction.
12
KOLBE’S REACTION
13
ACTION OF ZINC DUST
Phenol on heating with zinc dust produces benzene.
14
OXIDATION OF PHENOL
Phenol oxidation with
chromic acid (Na2Cr2O7+H2SO4 ) produces benzoquinone, which is a
conjugate diketone.
15
FRIES REARRANGEMENT
Uses
1
USES OF METHANOL
1. Methanol a colourless liquid with b.pt. 67∘C is used as solvent, paints,
varnishes, shellac etc., 2. Used in the manfacture of HCHO, perfumes and dyes. 3. Used in the preparation of methylated spirt, a mixture of recitified spirit
(95.6% ethyl alcohol + 4.4%water) and methyl alcohol making ethyl alcohol
unfit for drinking .
4. Two types of methylated spirits: a) mineralised spirit = 90% rectified
spirit + 9% methyl alcohol + 1% pyridine b) Surgical spirit = 95% rectified
spirit + 5% MeOH
5. In denaturation of ethyl alcohol, copper sulphate is added to give colour and pyridine is added to make it a foul smelling liquid. Because of denaturation, alcohol becomes unfit for drinking.
2
USES OF ETHYL ALCOHOL
1. As a solvent for pharmaceutical preparations, paints, perfumes, varnishes, gums etc., 2. In alcoholic bevarages. 3. As reaction medium, extractant and crystallsing 4. A source for the preparation of acetaldehyde, chloral, chloroform, iodoform, acetic acid ether etc. 5. A preservative for biological specimens, an antifreeze for automobile radiotors, a fuel in spirit lamps, stoves, a petrol substitute known as power
alcohol.
3
USES AND TESTS OF PHENOL
1) It is raw material for the manufacture of important dyes, drugs, pharmaceuticals, polymers and several other compounds. 2) It is strong antiseptic. 2,4-dichloro-3,5 dimethyl phenol is used as powerful antiseptic under the name Dettol. 3) It is used as a preservative for ink. 4) It is used in the manufacture of drugs like Aspirin, Salol etc. 5) It is used for causterising wounds caused by the bite of mad dogs. Tests of Phenol :
i) Aqueous solution of phenol gives violet colour with a drop a FeCl3.
ii) Aqueous phenol gives white precipitate with bromine water. iii) Phenol gives blue colour with ammonia and sodium hypochlorite.
4
USES : ETHER IS USED IN/AS
1. a solvent for oils, fats, waxes, plastics etc. 2. the extraction of organic compounds from aqueous solutions. 3. an inert medium for various reactions (ex.Wurtz reaction) and preparation of RMgX 4. an anaesthesia in surgery without causing any damage to heart or lungs. (Recently, HALOTHANE is widely used for this purpose since it is harmless
and quick in action. CF3CHClBr ) (IUPAC name : 2-Bromo-2- chloro-1,1,1-
trifluroethane) 5. NATALITE(mixture of Alcohol and Ether), a substitute for petrol 6. Refrigerant along with dry ice (solid CO2 ) which produces a temperature
around −110∘C
i) Enthrane ((CHFCl−CF2−O−CHF2) ) and isoflurane
((CF3)CHCl−O−CHF2 ) are used as anesthetics in place of diethyl ether as
the later one has slow effect. ii) Substituted anisols are used as flavourings and in perfumes due to their pleasant odour. Eg : 1.ANITHOLE is a constituent of anise seed. 2.EUGENOL is present in cloves. 3.VANILLIN is present in oil of vanilla been 4.THYMOL is present in thyme and mint are used as flavourings and in
perfumes.
Ethers
1
Structure of functional group-Ethers
In ethers, the four electron pairs, i.e, the two bond pairs and two lone pairs of electrons on oxygen are arranged approximately in a tetrahedral arrangment.
The bond angle is slightly greater than the tetrahedral angle due to the repulsive interaction between the two bulky (-R) groups. The C-O bond length (141 pm) is almost the same as in alcohols.
2
PREPARATION METHODS OF DIETHYL ETHER
1. FROM ETHYL ALCOHOL: Ethyl alcohol gives diethyl ether by acid -catalysed condensation reaction
C2H5OH+HOC2H5−→−−−−−−140∘Cconc.H2SO4C2H5OC2H5+H2O
The catalytic dehydration of ethanol with Al2O3 at 250−260∘C
2C2H5OH−→−−260∘CAl2O3C2H5OC2H5+H2O
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PREPARATION METHODS OF DIETHYL ETHER
2. WILLIAMSON SYNTHESIS : Ethyl halide reacts with Sodium or potassium ethoxide to form diethyl ether C2H5ONa+IC2H5→C2H5OC2H5+NaCl Alkyl halide is to be primary because with other alkyl halides alkenes are formed . Alkoxides are nucleophiles and strong bases.
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PREPARATION METHODS OF DIETHYL ETHER
3. From ethyl bromide: Ethyl bromide reacts with dry Silver oxide to from diethyl ether
C2H5Br+Ag−O−Ag+Br−C2H5→C2H5OC2H5+2AgBr
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CHEMICAL PROPERTIES OF ETHERS
Ethers are less reactive than alcohols due to non-availablity of active hydrogen.
Ethers do not react with alkali, acids, metals, phosphorous halides. Ethers do not oxidise and reduce easily like alcohols under normal
conditions. Ethers reacts with acids, phosphorous halides, oxidising agents and
reducing agents at high temperatures but cannot react with metals like sodium.
Reactions of ether are classified into three types on the basis of cleavage of bonds. i. ethyl groups which undergo substitution reactions. ii. ethereal oxygen which coordinates with electron deficient molecules like Lewis acids. iii. carbon- oxygen bond which shows some cleavage reaction.
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REACTIONS OF ETHER GROUP- HALOGENATION
Diethyl ether reacts with chlorine or bromine to from halogen substituted
ethers.Hydrogens at α carbon atoms are easily substituted in the dark
condition. CH3CH2OCH2CH3−→−−DarkCl2CH3CαH(Cl)−O−Cα′H(Cl)−CH3
(α,α′ dicholoro diethyl ether)
CH3CH2OCH2CH3−→−−−−sunlightCl2C2Cl5−O−C2Cl5
(perchloro diethyl ether)
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REACTIONS INVOLVING CLEVAGE OF C–O BOND
ACTION OF SULPHURIC ACID
C2H5−O−C2H5+H2SO4(Conc.)−→ΔC2H5OH+C2H5HSO4
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ACTION OF HYDROBROMIC ACID OR HYDROIODIC ACID
In the cold condition
C2H5−O−C2H5+HI→C2H5I+C2H5OH
In the hot condition with excess of HI
C2H5−O−C2H5+2HI−→Δ2C2H5I+H2O
Here the cleavage is at alkyl oxygen due to low reactiveity of aryl oxygen bond.In the cleavage of mixed ethers lower alkyl group forms alkyl iodide.
If 3∘ alkyl group is present it forms tertiary halide
as major product.
(CH3)3−C−OCH3+HI→CH3OH+(CH3)3−CI
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HYDROLYSIS
C2H5−O−C2H5+H2O→2C2H5OH
(steam)
Action of PCl5 C2H5−O−C2H5+PCl5→2C2H5Cl+POCl3
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ACTION OF ACETYL CHLORIDE AND ACETIC ANHYDRIDE
C2H5−O−C2H5+CH3COCl−→−−AlCl3C2H5Cl+CH3COOC2H5
C2H5−O−C2H5+(CH3CO)2O−→−−−ZnCl22CH3COOC2H5
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ACTION OF CARBON MONOXIDE
C2H5−O−C2H5+CO−→−−−−−900atmsBF3/150∘CC2H5COOC2H5
(ethylpropionate)
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OXIDATION OF ETHERS
C2H5OC2H5+(O)−→−−−−−−−acid.K2Cr2O72CH3CHO−→−−−−−−−acid.K2Cr2O72C
H3COOH
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DEHYDRATION OF ETHER
C2H5OC2H5−→−−−−−−−Al2O3/360∘C2CH2=CH2+H2O
