Study notes on ALCOHOL,PHENOL & ETHER., Study notes of Organic Chemistry

Download Study notes on ALCOHOL,PHENOL & ETHER. and more Study notes Organic Chemistry in PDF only on Docsity! 1196 Alcohol, Phenol and Ethers Hydroxy compounds Hydroxy compounds are those compounds in which the hydroxy group, – OH is directly linked with the aliphatic or aromatic carbon. Monohydric alcohols These are compound containing one hydroxyl group. Their general formula is OHC nn 22  (1) Preparation : (i) From alkyl halide KBrOHHCKOHBrHC  Ethanol 52 (Aqueous)eBromoethan 52 AgBrOHHCAgOHBrHC  Ethanol 52 oxidesilver MoisteBromoethan 52  1° alkyl halide gives good yield of alcohols.  2° alkyl halide gives mixture of alcohol and alkene.  3° alkyl halide gives alkenes due to dehydrohalogenation. duct)(Major pro eneMethylprop-2 3 2 | 3 (Aqueous) 3 3 | | 3 CH CHCCHKOH CH Br CHCCH  OHKBr CH OH CHCCH 2 product)dealcohol(si buty l Tert. 3 3 | | 3  (ii) From alkenes : (a) Hydration Direct process : Alcohol | | | |Alkene 42 HOH CCCC SOHdil HOH   Indirect process : sulphate hydrogenEthyl 223 acidSulphuric 2 Ethene 22 OHOSOCHCHOHHOSOCHCH  42 Ethanol 23 Boil 2 SOHOHCHCH OH   In case of unsymmetrical alkenes rule s'ffMarkowniko 2 Propene 23   OHHOSOCHCHCH ol-2-Propan 3 | 3 Boil 2 3 | 3 2 CH OH CHCH OHOSO CHCHCH OH   (b) Oxymercuration-demercuration   tionOxymercura acetateMercuric 22 )(OAcHgOHCC Alcohol ||ionDemercurat | | | | 4 HOH CC HgOAc C OH C NaBH   This reaction is very fast and produces the alcohol in high yield. The alcohol obtained corresponds to Markownikoff’s addition of water to alkene. (c) Hydroboration oxidation (HBO) : (Antimarkownikoff’s orientation) 2 , | | | | 2 22 BH C H CBHHCC OHOH    Alcohol | | | | OHH CC  Diborane is an electron defficient molecule. It acts as an electrophile reacting with alkenes to form alkyl boranes BR3 .    OH CH CHC 2 3 3 |    42 3 2 | SOH CH HCHC Alcohol 3 3 | | CH OH CHC Alcohol, Phenol and Ether Chapter 26 Alcohol, Phenol and Ethers 1197    2 neAlkyl bora 2 2 || 22 CHRCH HB HC H CHRBHHCHCHR oraneTrialkyl b 322 raneDialkyl bo 222 )()( 2 BCHRCHBHCHCHR CHRCH     Carbocation are not the intermediate in HBO hence no rearrangement take place. (iii) By reduction of carbonyl compounds alcohol Primary 22 Aldehyde 4 OHRCHHRCHO LiAlH Pd  alcohol Secondary |/or 2 Ketone 4 R OH CHRHRRCO PtNi NaBH   4LiAlH also reduces epoxides into alcohol : OHCHCHLiAlH O CHCH 23422  Hydride selectively attacks the less alkylated carbon of the epoxide. 3 3 | | 3 3 2 | 3 4 CH OH CHCCH H CH O CHCCH H LiAlH    (iv) By reduction of carboxylic acids and their derivatives alcohol primary 2 (ii) (i) acid Carboxylic 2 4 OHRCHCOOHR OH LiAlH   OHROHRCHRRCOORCOOH H  2 CatalystEsteracid Carboxylic 2 Esters are also reduced to alcohols (Bouveault Blanc reaction) Methanol 3 Ethanol 23 / (Ester) acetateMethy l 3 || 3 52][4 OHCHOHCHCHHOCH O CCH OHHCNa    Reduction with aluminium isopropoxide is known as Meerwein-Ponndorff verley reduction (MPV) reduction.   )( alcoholIsopropyl 232 2)( OCHMeAl CHOHCHOCMe OC CH CH CHOHMe  3 3 2 (v) By alkaline hydrolysis of ester Alcoholacidof salt Sod. |||| )aq( OHRONa O CRNaHORO O CR  . (vi) From primary amines   HClNaNO HONONHCHCH / eAminoethan 223 2 OHNOHCHCH 22 Ethanol 23   It is not a good method of preparation of alcohols because number of by product are formed like alkyl chloride alkenes and ethers. (vii) From Grignard reagent (a) With oxygen : XMgOROXMgR OAl   22 32 2 . OHXMgROH HOH )(22 2   (b) With ethylene oxide :        O CHCHXMgR 22 OHXMgOHCHRCHOMgXCHRCH OH )(2222 2   (c) With carbonyl compounds : OH R H CR OMgX R H CR H O CRXMgR OH      | | | | | || 2     If R = H, product will be 1°alcohol.  If R = R, product will be 2°alcohol.  If carbonyl compound is a ketone, product will be 3° alcohol.  It is the best method for preparation of alcohol because we can prepare every type of alcohols. (viii) The oxo process : It is also called carbonylation or hydroformylation reaction. A mixture of alkene carbon monoxides and hydrogen. Under pressure and elevated temperature in the presence of catalyst forms aldehyde. Catalyst is cobalt carbonyl hydride ])([ 4COCoH product is a mixture of isomeric straight chain (major) and branched chain (minor) aldehydes. Aldehydes are reduced catalytically to the corresponding alcohols.  223 222 HCOCHCHCH (2) Physical properties of monohydric alcohols (i) Character : Alcohols are neutral substances. These have no effect on litmus paper. This is analytical test for alcohols. B2H6 CH3 CH3   CH3 HO H3O+ HO – CH2 CH2OH CH2 CH2 CH3 OH H2O CH3 – CH – CHO | CH3 (Minor) CH3 – CH – CH2OH | CH3 Isobutyl alcohol H2 Zn – Cu CH3 – CH2 – CH2 – CH2 – OH n- Butyl alcohol (Major) 223 CHOCHCHCH  H2 Zn – Cu 1200 Alcohol, Phenol and Ethers OH CHCHCHCH OH CHHCCHCH | 3233 | 2     3 3 3 | | 3 3 3 3 | | | 3 2 42 CH CH CH CHCCH CH OHCH CHCHCCH OH SOH alkene-2 3 3 3 | 3 33 3 || 3 CH CH C CH CCH CHCH CHCHCCH H     (iv) General reaction of alcohols (a) Reduction : 222 IOHHRHIOHR   (b) Oxidation : Difference between 1°, 2° and 3° alcohols. 1°  acid Carboxylic | Aldehyde | 2 O OH CRO H CROHRCH  2°  R O CRR OH CHR CrO   || alcoholSecondary | 3 OHCORCOOH O 22 conditionsDrastic   3°  atoms) carbonof number (Lesser Acetone 3 | 3 )condition strong Under ( ][4 (Tertiary ) alcohol buty l Tert. 3 3 | | 3 CH OCCH CH CH OHCCH O   OHCOCOOHCH O 22 atoms) carbonof number(Lesser acidAcetic 3 )condition strong Under ( ][4    3° alcohols are resistant to oxidation, but on taking stronger oxidising agent they form ketone. (c) Catalytic oxidation/dehydrogenation 1° 2 y de)(Acetaldeh Ethanal | 3 573, alcohol) (Pri. Ethanol | | 3 HO H CCHHO H H CCH KCu   2° (Acetone) Propanone 3 2 | 3 573, 3 alcohol) (Sec. Propanol-2 | | 3 CH HOCCH CH HO H CCH KCu   3° OH CH CHCCH CH CH OHCCH KCu 2 (Alkene) eneMethy lprop-2 3 2 | 3 573, alcohol) (Tert. ol-2-anMethy lprop-2 3 3 | | 3   Important reagents used for oxidation of alcohols  PCC [Pyridinium chloro chromate )( 356   CrOClHNHC ] to oxidise 1° alcohols to aldehydes and 2° alcohols to ketones.  PDC [Pyridinium di chromate  2 72 2 255 ).( OCrNHHC ] to oxidise 1° alcohols to aldehyde and 2° alcohol to ketones.  42CrOH (chromic acid) to oxidise 1° alcohol to carboxylic acid.  423 SOHCrO  / Acetone to oxidise 2° alcohol to ketones.  Jones reagents (chromic acid in aqueous acetone solution) oxidise 1° alcohol to aldehyde and 2° alcohol to ketone without affecting (C = C) double bond.  2MnO selectively oxidises the –OH group of allylic and benzylic 1° and 2° alcohols to give aldehyde and ketone respectively.  42ON in 3CHCl oxidises primary and secondary benzyl alcohol. (d) Self condensation : Guerbet’s reaction OHCH R CHHOHCHCHR  2 | 22 alcoholhigher 2 | 22 ,52 OHCH R CHCHCHR HNaOC    (e) Reaction with cerric ammonium nitrate :  ROH colour Yellow nitrate ammoniumCerric Red colour solution of complex. This is analytical test for alcohols. (f) Iodoform test : When a few drops of alcohol are warmed with iodine and NaOH yellow precipitate of iodoform with characteristic smell is obtained. Any alcohol consists CHOHCH3 group give iodoform test. Since reaction takes place with alkali solution as one of the reagents hence alkyl halide like ClCHCH 23  and R Cl CHCH  | 3 will also give this test. (4) Uses of monohydric alcohol : (i) Uses of ethanol : It is used (a) In alcoholic beverages, (b) As a solvent in paints, varnishes, oils, perfumes etc., (c) In the preparation of chemical like chloroform, ether etc., (d) As a fuel in spirit lamps, (e) As an antifreeze for automobile radiators, (f) In the scientific apparatus like spirit levels, (g) As power alcohol. (ii) Uses of methanol : 32 CHCHCHCH  t CHCHCHCH amounMore 32  322 CHCHCHCH   OH CHCHCHCH | 322  H+ H2SO4 – H2O Alcohol, Phenol and Ethers 1201 (a) Methanol is an important industrial starting material for preparing formaldehyde, acetic acid and other chemicals. (b) As a fuel (a petrol substitute). A 20% mixture of methyl alcohol and gasoline is a good motor fuel. (c) As an antifreeze or automobile radiators. (d) To denature ethyl alcohol. The mixture is called methylated spirit. (e) In the preparation of dyes, medicines and perfumes. Methyl salicylate and methyl anthra anilate are used in perfumery. Table : 26.1 Difference between methanol and ethanol Methanol Ethanol (i) When CH3OH is heated on Cu coil it gives formalin like smell. (i) It does not give formalin like smell. (ii) When CH3OH is heated with salicylic acid in H2SO4 (conc.) then methyl salicylate is formed which has odour like winter green oil. (ii) No such odour is given. (iii) It does not give haloform or iodoform test. (iii) It gives haloform test Interconversion of monohydric alcohols (i) Primary alcohol into secondary alcohols Propene 23 alc 73 alcohol) (1 ol-1-Propan 73 2 CHCHCHClHCOHHC KOHSOCl     alcohol) (2 ol2--Propan 3 | 3 aq. 3 | 3     CH OH CHCHCH Br CHCH KOHHBr (ii) Secondary alcohol into tertiary alcohol 3 || 3 / ][ alcohol) (2 alcohol)propyl -(Iso ol2--Propan 3 | 3 722 CH O CCHCH OH CHCH HOCrK O    alcohol) buty l (tert. )(3 ol-2-anMethy lprop-2 3 3 | | 3 , 3 3 | | 3 23      OH CH CHCCH OMgBr CH CHCCH OHHMgBrCH (iii) Primary alcohol into tertiary alcohol rule sff'Markowniko 3 2 | 3 nDehydratio Heat , alcohol) buty l (Iso )(1ol -1-anMethy lprop2- 3 2 | 3 42     HBrSOH CH CHCCHOH CH CHCHCH alcohol) buty l (tert. )(3ol 2--anMethy lprop2- 3 3 | | 3 aq. 3 3 | | 3    CH OH CHCCH CH Br CHCCH KOH (iv) Lower alcohol into higher alcohol (ascent of series) CNCHICHOHCH KCNHI 33 atom) carbon (1 Methanol 3   atoms) carbon (2 Ethanol 23223 Reduction )(4 OHCHCHNHCHCH HONOH    (v) Higher alcohol into lower alcohol [Descent series] COONaCHCOOHCHOHHC NaOH O HOCrK 33 ][ , atoms) carbon (2 Ethanol 52 722     atom) carbon (one Methanol 3 aq. 34 Heat 2 OHCHClCHCH KOHClCaONaOH      Distinguish between primary, secondary and tertiary monohydric alcohols (i) Lucas test : A mixture of anhydrous HClZnCl conc.2  is called as Lucas reagent. Primary    ClCHROHCHR OH ZnClHCl 2 anhy . / conc. 2 2 2 ppt. appears after heating Secondary    ClCHROHCHR OH ZnClHCl 2 anhy . / conc. 2 2 2 ppt. appears with in 5 minutes Tertiary   ClCROHCR HClZnCl 3 / 3 2 ppt. appears immediately (ii) Victor mayer test : Also known as RBW test. RBW  Red, Blue, White test. Primary colour) (Red acidnitrolic of salt Sod. 2 || 3 acidNitrolic 2 || 32525252 22 NONa NOCCH NOH NOCCHNOHCIHCOHHC NaOHHONOAgNOIP       Secondary       NaOHHONOAgNOIP O NO NCCH H NOCCHCHICHCHOHCH 2 | 232 | 232323 )()()()( 22 No reaction (Blue colour) Tertiary      HONOAgNOIP CNOCHClCHCOHCH 2333333 )()()( 22 No reaction (colourless) Dihydric alcohols 1202 Alcohol, Phenol and Ethers These are compound containing two hydroxyl groups. These are dihydroxy derivatives of alkanes. Their general formula is 222 OHC nn  . The simplest and most important dihydric alcohol is ethylene glycol. They are classified as , , ….. glycols, according to the relative position of two hydroxyl groups.  is 1, 2 glycol,  is 1, 3 glycol. (1) Preparation (i) From ethylene : (a) Through cold dilute alkaline solution of Bayer’s reagent (b) With O2 in presence of Ag : glycol Ethy lene 2 | 2 dil. oxide Ethy lene 2 | 2 400200, Cataly st 2 Ethy lene 2 || 2 2 2 1 OHCH OHCH O CH CH O CH CH HCl OH CAg     (c) With HOCl followed by hydrolysis : (Industrial method) inchlorohydr Ethy lene 2 | 2 2 || 2 ClCH OHCH HOCl CH CH  2 Glycol 2 | 2 3 CONaCl OHCH OHCH NaHCO   (ii) From 1, 2 dibromo ethane [Lab method]: 2 2 | 2 232 2 | 2 2 CONaBr OHCH OHCH OHCONa BrCH BrCH  diacetateGlycol 32 | 32 2 3 2 | 2 32 OOCCHCH OOCCHCH COOKCH BrCH BrCH KBr COOHCH    COONaCH OHCH OHCH NaOH 3 2 | 2 2  (2) Physical properties (i) It is a colourless, syrupy liquid and sweet in taste. Its boiling point is 197°C. (ii) It is miscible in water and ethanol in all proportions but is insoluble in ether. (iii) It is toxic as methanol when taken orally. (iv) It is widely used as a solvent and as an antifreeze agent. (3) Chemical properties | | – C=C – (i) dil. KMnO4 (ii) dil. OH– | | – C = C – | | OH OH (Syn- hydroxylation) RCO2OH H2O H+ OH | | – C – C – | | OH (Anti- hydroxylation) | | – C – C – O Na 50° C CH2Cl | CH2 OH PCl5 CH2 Cl | CH2 Cl 1,2 Dichloroethane CH2 ONa | CH2 OH CH2 ONa | CH2 ONa Dialkoxide (Disodium glycollate) N a 160° C CH2Br CH2Br PCl 5 Chlorohydrin Alcohol, Phenol and Ethers 1205 Unsaturated alcohols (Allyl alcohol) (1) Preparation (i) From allyl halide alcoholAllyl 22222 HBrOHCHCHCHOHBrCHCHCH  (ii) By heating glycerol with oxalic acid : alcoholAlly l 2 2 || |2 Heat 2 2 || | 2 | 2 2 | | 2 2 CH OHCH CH OOCCH OHCH COOCH HOOC HOOC OHCH OHCH OHCH CO OH      (2) Physical properties (a) It is colourless, pungent smelling liquid. (b) It is soluble in water, alcohol and ether in all proportion. (3) Chemical properties Phenol (Carbolic acid), C6H5OH or Hydroxy benzene It was discovered by Runge in the middle oil fraction of coal-tar distillation and named it ‘carbolic acid’ (carbo = coal, oleum = oil) or phenol containing 5% water is liquid at room temperature and is termed as carbolic acid. It is also present in traces in human urine. (1) Preparation (i) From benzene sulphonic acid    NaOHfSOH HSOHCHC acidsulphonic Benzene 356 )uming( Benzene 66 42 Phenol 56 /or / phenoxideSodium 56 Fusesulphonate benzeneSodium 356 22 2 OHHCONaHCNaSOHC OHCO OHHNaOH     This is one of the laboratory methods for the preparation of phenol. Similarly methyl phenols (cresols) can be prepared. (ii) From benzene diazonium chloride Aniline 256 / neNitrobenze 256 45,Benzene 66 42 3 NHHCNOHCHC HClSn CSOH HNO o    Phenol 56 WarmchloridediazoniumBenzene 256 50, 22 OHHCClNHC OH CHCl NaNO o      Diazonium salts are obtained from aniline and its derivatives by a process called diazotisation. (iii) From Grignard reagent bromidemagnesiumPhenyl 56 Ether neBromobenze 56 MgBrHCMgBrHC   Phenol 5656 22 OHHCOMgBrHC H OHO    (iv) From salicylic acid : (v) Middle oil of coal tar distillation : Middle oil of coal-tar distillation has naphthalene and phenolic compounds. Phenolic compounds are isolated in following steps. Step I : Middle oil is washed with 42SOH . It dissolves basic impurities like pyridine (base). Step II : Ecessive cooling separates naphthalene (a low melting solid) H2 Pt CH3CH2CH2OH 1-propanol CH2 = CH – CH2OH – (Allyl alcohol) CH2Br – CHBrCH2OH 2, 3-dibromopropanol-1 Br2 CH2BrCH2 CH2OH 3-Bromopropanol-1 HBr CH2OHCHClCH2OH Glycerol -monochlorohydrin HOCl CH2 OH – CHOH – CH2OH Glycerol Alk. KMnO4 (O + H2O) CH2 = CH – CH2OOCCH3 Allyl acetate CH3COOH CH2 = CH – CH2Cl Allyl chloride HCl COOH | COOH Oxalic acid HCOOH Formic acid + Oxidati on Na CH2 = CH – CH2ONa CH2 – CH – CH2 | | | Br Br OH CH2 – CH – COOH | | Br Br Zn dust (CH3OH ) CH2 = CH – COOH Acrylic acid [O] HNO 3 Br2 SO3H CH3 p-Toluene sulphonic acid OK CH3 OH CH3 p- Cresol Solid KOH Fuse H+/H2O OH COOH Salicylic acid + 2NaOH CaO OH Phenol + Na2CO3 + H2O NH2 CH3 m- Toluidine N2Cl CH3 m-Toluene diazonium chloride H2O OH CH3 m- Cresol HNO 2 HCl 1206 Alcohol, Phenol and Ethers Step III : Filtrate of step II is treated with aqueous NaOH when phenols dissolve as phenoxides. Carbon dioxide is then blown through the solution to liberate phenols. OHONaHCNaOHOHHC 25656  3256 , 22 CONaOHHC OHCO   Step IV : Crude phenol (of step III) is subjected to fractional distillation. (vi) Raschig’s process OHClHCOHClHC C FeClCuCl o 2 eneChlorobenz 56 250 / 2 Benzene 66 32 2 1   HClOHHCOHClHC Co   Phenol 56 425 steam 2 eneChlorobenz 56 (vii) Dow process OHNaClONaHCNaOHClHC Co 256 pressureHigh 300 eneChlorobenz 56 2   sodium phenoxide on treatment with mineral acid yields phenol. 42564256 22 SONaOHHCSOHONaHC  (viii) Oxidation of benzene OHHCOHC C OV o 56 315 266 22 52  (ix) Oxidation of isopropyl benzene [Cumene] (2) Physical properties (i) Phenol is a colourless crystalline, deliquescent solid. It attains pink colour on exposure to air and light. (ii) They are capable of forming intermolecular H- bonding among themselves and with water. Thus, they have high boiling points and they are soluble in water. Due to intermolecular H- bonding and high dipole moment, melting points and boiling points of phenol are much higher than that of hydrocarbon of comparable molecular weights. (iii) It has a peculiar characteristic smell and a strong corrosive action on skin. (iv) It is sparingly soluble in water but readily soluble in organic solvents such as alcohol, benzene and ether. (v) It is poisonous in nature but acts as antiseptic and disinfectant. (3) Chemical properties (i) Acidic nature : Phenol is a weak acid. The acidic nature of phenol is due to the formation of stable phenoxide ion in solution. OHOHHC 256  ⇌   OHOHC 3 ion Phenoxide 56 The phenoxide ion is stable due to resonance. The negative charge is spread throughout the benzene ring. This charge delocalisation is a stabilising factor in the phenoxide ion and increase acidity of phenol. [No resonance is possible in alkoxide ions (RO–) derived from alcohols. The negative charge is localised on oxygen atom. Thus alcohols are not acidic].  Phenols are much more acidic than alcohols but less so than carboxylic acids or even carbonic acid. This is indicated by the values of ionisation constants. The relative acidity follows the following order Alcohols 18 Water 14 Phenol 56 10 acidCarbonic 32 7 acid Carboxy lic 5 )10()10()10()10()10()approx.( ROHHOHOHHCCOHRCOOH Ka   Effects of substituents on the acidity of phenols : Presence of electron attracting group, (e.g., 2NO , – Crude phenols fraction al distillati on 180°C 211°- 235°C o, m, p-cresols xylols (hydroxy xylenes) AlCl3 AlCl3 + CH3CH2CH2Cl + CH3CH = CH2 CH Cumene CH3 H3C O2 Cataly st O – OH | C(CH3)2 Cumene hydroperoxi de H2O/H + OH Phenol + (CH3)2CO Acetone H – O-------H – O-------H – O-------H – O------- + – + – + – + – (intermolecular H-bonding among phenol H H | | H – O-------H – O-------H – O-------H – O------- + – + – – + + – (crossed intermolecular H-bonding between water and phenol molecules) O .. – O– O .. – O .. – Alcohol, Phenol and Ethers 1207 X,  3NR , –CN, –CHO, –COOH) on the benzene ring increases the acidity of phenol as it enables the ring to draw more electrons from the phenoxy oxygen and thus releasing easily the proton. Further, the particular effect is more when the substituent is present on o- or p-position than in m-position to the phenolic group. The relative strengths of some phenols (as acids) are as follows : p-Nitrophenol > o-Nitrophenol > m- Nitrophenol > Phenol Presence of electron releasing group, (e.g., 3CH , 2352 ,, NROCHHC  ) on the benzene ring decreases the acidity of phenol as it strengthens the negative charge on phenoxy oxygen and thus proton release becomes difficult. Thus, cresols are less acidic than phenol. However, m-methoxy and m-aminophenols are stronger acids than phenol because of –I effect and absence of +R effect. m-methoxy phenol > m-amino phenol > phenol > o-methoxy phenol > p-methoxy phenol Chloro phenols : o- > m- > p- Cresols : m- > p- > o- Dihydric phenol : m- > p- > o- The acidic nature of phenol is observed in the following : (a) Phenol changes blue litmus to red. (b) Highly electropositive metals react with phenol. 25656 222 HONaHCNaOHHC  (c) Phenol reacts with strong alkalies to form phenoxides. OHONaHCNaOHOHHC 25656  However, phenol does not decompose sodium carbonate or sodium bicarbonate, i.e., 2CO is not evolved because phenol is weaker than carbonic acid. (ii) Reactions of –OH group (a) Reaction with FeCl3 : Phenol gives violet colouration with ferric chloride solution (neutral) due to the formation of a coloured iron complex, which is a characteristic to the existence of keto-enol tautomerism in phenols (predominantly enolic form). This is the test of phenol. (b) Ether formation : Phenol reacts with alkyl halides in alkali solution to form phenyl ethers (Williamson’s synthesis). The phenoxide ion is a nucleophile and will replace halogenation of alkyl halide. OHONaHCNaOHOHHC 2 phenoxideSod. 5656  NaClOCHHCClCHONaHC  (Anisole)ether nyl Methyl phe 356356 KIHCOHCHICOKHC  (Phenetol) benzeneEthoxy 52565256 etherphenyl Isopropyl 2356 chlorideIsopropyl 2356 )()( CHHCOHCCHHCClONaHC  Ethers are also formed when vapours of phenol and an alcohol are heated over thoria )( 2ThO or 32OAl . benzeneMethoxy 356 , 356 2 CHOHCHOCHOHHC ThO    (c) Ester formation : Phenol reacts with acid chlorides (or acid anhydrides) in alkali solution to form phenylesters (Acylation). This reaction (Benzoylation) is called Schotten-Baumann reaction. OHONaHCNaOHOHHC 25656  NaClOOCCHHCCH O CClONaHC  acetatePheny l 356 chlorideAcety l 3 || phenoxideSodium 56   NaOH OCOCHOHHC anhydrideAcetic 2356 )( COOHCHOOCCHHC 3 (ester) acetatePhenyl 356    NaOH HC O CClOHHC chlorideBenzoy l 56 || 56 OHNaClHC O COHC 2 zoatePheny l ben 56 || 56  The phenyl esters on treatment with anhydrous 3AlCl undergoes Fries rearrangement to give o- and p- hydroxy ketones. (d) Reaction with PCl5 : Phenol reacts with 5PCl to form chlorobenzene. The yield of chlorobenzene is poor and mainly triphenyl phosphate is formed. HClPOClClHCPClOHHC  356556 OH Enol O Keto OH 6 + FeCl3  3H+ + Fe O 6 3– + 3HCl OOCCH3 Phenyl acetate AlCl3 (anhydrous) hea t + OH COCH3 OH COCH3 hydroxy acetophenone p- o - 1210 Alcohol, Phenol and Ethers Phenol couples with phthalic anhydride in presence of concentrated 42SOH to form a dye, (phenolphthalein) used as an indicator. (b) Condensation with formaldehyde : Phenol condenses with formaldehyde (excess) in presence of sodium hydroxide or acid )( H for about a week to form a polymer known as bakelite (a resin). (c) Liebermann’s nitroso reaction : When phenol is reacted with 2NaNO and concentrated 42SOH , it gives a deep green or blue colour which changes to red on dilution with water. When made alkaline with NaOH original green or blue colour is restored. This reaction is known as Liebermann’s nitroso reaction and is used as a test of phenol. (d) Oxidation : Phenol turns pink or red or brown on exposure to air and light due to slow oxidation. The colour is probably due to the formation of quinone and phenoquinone. But on oxidation with potassium persulphate in alkaline solution, phenol forms 1, 4-dihydroxy benzene (Quinol). This is known as Elbs persulphate oxidation. (4) Uses : Phenol is extensively used in industry. The important applications of phenol are  O || C – OH C – OH || O Phthalic acid H OH H OH O || C C || O O Phthalic anhydride Phenol (2 molecules) Conc. H2SO4 (– H2O) O || C C O OH OH Phenolphthale in [O ] CrO2Cl 2 + H2O O p- benzoquinone O OH Phenol OH OH Quinol K2S2O8 in alkaline solution OH Pheno l + OH OH CH2OH o-hydroxy benzyl alcohol NaO H + CH2O OH CH2OH p-hydroxy benzyl alcohol Condensation with HCHO continues give OH CH2 CH2 CH2 OH CH2 CH2 Polymer Bakelite (a resin) HONO OH p- Nitrosophenol OH NO O NO H Quinoxi m O N OH + H OH H2SO 4 H2O O N OH NaO H –H2O Sod. Salt of indophenol (blue) Indo phenol (Red) OH O2 by air o CrO3 O O p- benzoquinone C6H5OH OH - - - O O - - - HO Phenoquinone (pink) C6H5OH or Alcohol, Phenol and Ethers 1211 (i) As an antiseptic in soaps, lotions and ointments. A powerful antiseptic is “Dettol” which is a phenol derivative (2, 4-dichloro-3, 5-dimethyl phenol). (ii) In the manufacture of azo dyes, phenolphthalein, etc. (iii) In the preparation of picric acid used as an explosive and for dyeing silk and wool. (iv) In the manufacture of cyclohexanol required for the production of nylon and used as a solvent for rubber and lacquers. (v) As a preservative for ink. (vi) In the manufacture of phenol-formaldehyde plastics such as bakelite. (vii) In the manufacture of drugs like aspirin, salol, phenacetin, etc. (viii) For causterising wounds caused by the bite of mad dogs. (ix) As a starting material for the manufacture of nylon and artificial tannins. (x) In the preparation of disinfectants, fungicides and bactericides. (5) Tests of phenol (i) Aqueous solution of phenol gives a violet colouration with a drop of ferric chloride. (ii) Aqueous solution of phenol gives a white precipitate of 2, 4, 6-tribromophenol with bromine water. (iii) Phenol gives Liebermann’s nitroso reaction. Phenol in conc. sulphuric acid of water Excess 2  NaNO Red colour (Excess)   NaOH Blue colour (iv) Phenol combines with phthalic anhydride in presence of conc. 42SOH to form phenolphthalein which gives pink colour with alkali, and used as an indicator. (v) With ammonia and sodium hypochlorite, phenol gives blue colour. Table : 26.2 Difference between phenol and alcohol Property Phenol (C6H5OH) Alcohol (C2H5OH) Odour Typical phenolic odour Pleasant alcoholic odour Nature, reaction with alkali Acidic, dissolves in sodium hydroxide forming sodium phenoxide. Neutral, no reaction with alkalies. Reaction with neutral FeCl3 Gives violet colouration due to formation of complex compound. No reaction. Reaction with halogen acids No reaction with halogen acids. Forms ethyl halides. Oxidation Pink or brown colour due to formation of quinone and phenoquinone. Undergoes oxidation to give acetaldehyde and acetic acid. Reaction with HCHO Forms polymer (bakelite). No reaction. Liebermann’s nitroso reaction Positive. Does not show. Coupling with benzene diazonium chloride Forms azo dye. Does not form any dye. Reaction with PCl5 Mainly forms triphenyl phosphate. Forms ethyl chloride Iodoform test Does not show. Positive. Derivatives of phenol NITROPHENOLS (1) Preparation (ii) lnitropheno- and - 2 46 120 nenitrobenze chloro- and - 2 46 po C NaOH po NO OH HC NO Cl HC    (iii) lnitropheno- and - 2 46 heat Solid neNitrobenze 256 po KOH NO OH HCNOHC   OH OH NO2 o-isomer (steam volatile) Dil. HNO3 OH NO2 p-isomer (non-volatile) + 1212 Alcohol, Phenol and Ethers (iv) (2) Properties : o-Nitrophenol is a yellow coloured crystalline compound, while m- and p-isomers are colourless crystalline compounds. 1149745C)( m.pt. Isomer parametaortho  The lowest melting point of o-isomer is due to intramolecular hydrogen bonding whereas meta and para isomers possess intermolecular hydrogen bonding and thus, they have higher melting points. They are stronger acids than phenol. The order is : p-isomer > o-isomer > m-isomer > phenol When reduced, they form corresponding aminophenols. o- and p-Nitrophenols react with bromine water to form 2, 4, 6-tribromophenol by replacement of nitro group. Picric acid (2, 4, 6-trinitrophenol) (1) Preparation : It is obtained when phenol is treated with conc. 3HNO . However, the yield is very poor. It is prepared on an industrial scale : (i) From chlorobenzene (ii) From phenol through disulphonic acid (iii) (2) Properties : It is a yellow crystalline solid, melting points 122°C. it is insoluble in cold water but soluble in hot water and in ether. It is bitter in taste. Due to the presence of three electronegative nitro groups, it is a stronger acid than phenol and its properties are comparable to the carboxylic acid. It neutralises alkalies and decomposes carbonates with evolution of carbon dioxide. Dry picric acid as well as its potassium or ammonium salts explode violently when detonated. It reacts with 5PCl to form picryl chloride which on shaking with 3NH yields picramide. When distilled with a paste of bleaching powder, it gets decomposed and yields chloropicrin, 23 NOCCl , as one of the products and is thus employed for the manufacture of tear gas. It forms yellow, orange or red coloured molecular compounds called picrates with aromatic hydrocarbons, amines and phenols which are used for characterisation of these compounds.  Picrates are explosive in nature and explode violently when heated. These are prepared carefully. NH4HS or Na2S NO2 m- Dinitrobenzen e NO2 NO2 m-Nitroaniline NH2 NaNO2/HCl 0-5°C NO2 m-Nitrobenzene diazonium chloride N2Cl H2O NO2 m-Nitrophenol OH OH Br Br Br   2 isomer-or - 2 46 \ / Br po NO OH HC 2,4,6 Tribromophenol Cl HNO3 H2SO4 Chlorobenze ne 2, 4- Dinitrochlorobenzene Cl NO2 NO2 Aq. Na2CO3 OH NO2 Picric acid (2, 4, 6- Trinitrophenol) O2N NO2 OH NO2 NO2 HNO3 H2SO4 OH NO2 Picric acid O2N NO2 H2SO4 OH Phenol Phenol disulphonic acid OH SO3H SO3H HNO3 Picric acid OH NO2 O2N NO2 Ke3Fe(CN) 6 NO2 O2N NO2 + [O] TNB OH NO2 O2N NO2 PCl5 H2O NH3 Picryl chloride Cl NO2 O2N NO2 Picramide NH2 NO2 O2N NO2 Alcohol, Phenol and Ethers 1215 Ethers are anhydride of alcohols, they may be obtained by elimination of a water molecule from two alcohol molecules. OHRORRHOOHR 2 Ether  General formula is OHC nn 22  General methods of preparation of ethers (1) From alkyl halides (i) Williamson’s synthesis It is a nucleophilic substitution reaction and proceed through 2N S mechanism. NaXRROXRRONa  NaIHOCCHICHONaHC  ethermethyl Ethyl 5233 ethoxide Sodium 52 NaBrHOCHCBrHCONaHC  neEthoxyetha 5252 ideEthyl brom 52 ethoxide Sodium 52 (a) Order of reactivity of primary halide is XCHCHCHXCHCHXCH 223233  . (b) Tendency of alkyl halide to undergo elimination is ooo 123  . (c) For better yield alkyl halide should be primary and alkoxide should be secondary or tertiary. ether buty l .Ethy l tert 3 3 3 | | 52 alcohol buty l tert. of salt Sodium 3 3 3 | |ideEthyl brom 52 CH CH CHCOHC CH CH CHCNaOBrHC  (d) Secondary and tertiary alkyl halides readily undergo 2E elimination in the presence of a strong base to form alkenes. 3 3 | | 3 3 3 | | 3 52 CH CH ClCCH CH CH ClCCH ONaHC   , 3 2 52 | || 3 3 2 52 | | 3 CH CH OHHCCCH CH HCH OHCCCH      Aryl halide and sodium alkoxide cannot be used for preparing phenolic ethers because aryl halide are less reactive toward nucleophilic substitution reaction than alkyl halides. (ii) By heating alkyl halide with dry silver oxide AgXROROAgRX 22 heat 2   , AgBrHOCHCOAgBrHC 22 etherDiethyl 5252 heat 2 ideEthyl brom 52   (2) From alcohols (i) By dehydration of alcohols (a) With conc. H2SO4 at 140° C OHRORHORROH C SOH o 2 Ether140 )conc.( alcoholof molecules 2 42   .  In this reaction alcohol must be present in excess.  This reaction is mainly applicable for the dehydration of primary alcohols. Secondary and tertiary alcohols form alkenes mainly.  When this reaction is carried out between different alcohols then there is a mixture of different ethers is obtained. (b) With Al2O3 at 250° C : OHRORROH C OAl o 2 250 322   (ii) By the action of diazomethane on alcohols : This reaction is in presence of catalyst, boron trifluoride or 4HBF . 2322 3 NCHORNCHROH BF   (a) This method is very useful for preparing mixed ethers. (b) In higher cases, there can be 1, 2-hydride or 1, 2-methyl shift to form more stable carbonium ion. (3) Alkoxy mercuration-demercuration acetate rifluoroMercuric t 23 alkene ][OOCCFHgOHRCC  Ether | | | | 3 | | | | 4 HOR CC HgOOCCF C OR C NaBH    This is the best method for the preparation of t- ethers. (4) Reaction of lower halogenated ether with grignard reagent 2 ether Higher 2 reagant Grignard ether dHalogenate 2 MgXRROCHRXMgXROCH  (i) Higher members can be prepared by the action of grignard reagent on lower halogenated ethers. (ii) Ether form soluble coordinated complexes with grignard reagent. Physical properties (1) Physical state : Methoxy methane and methoxy ethane are gases while other members are volatile liquid with pleasant smell. (2) Dipole moment (D.M.) : Bond angle of ether is due to 3sp hybridisation of oxygen atom. Since C – O bond is a polar bond, hence ether possess a net dipole moment, even if they are symmetrical. dipole moment of dimethyl ether is 1.3 D and dipole moment of di ethyl ether is 1.18 D.  The larger bond angle may be because of greater repulsive interaction between bulkier alkyl groups as compared to smaller H-atoms in water. 1216 Alcohol, Phenol and Ethers (3) Boiling points : Boiling points of ethers are much lower than those of isomeric alcohols, but closer to alkanes having comparable mass. This is due to the absence of hydrogen bonding in ethers. (4) Solubility : Solubilities of ethers in water are comparable with those of alcohols. Example : Di ethyl ether and n-butyl alcohol have approximately the same solubility in water. This is because, ether form hydrogen bond with water much in the same way as alcohol do with water. Ether Water Ether ........... .......... R R OH OHO R R  Solubility of ether in water decreases with the size of alkyl groups. (5) Hydrogen bonding : There is no hydrogen directly attach (bonded) to oxygen in ethers, so ethers do not show any intermolecular hydrogen bonding. alcohols innding hydrogenbo ||| --------- R OH R OH R OH  ether in bondhydrogen No ROR  (6) Density : Ethers are lighter than water. Chemical properties : Ethers are quite stable compounds. These are not easily attacked by alkalies, dilute mineral acids, active metals, reducing agents or oxidising agents under ordinary conditions. (1) Reaction due to alkyl group (i) Halogenation : )etherdiethyl Monochloro-( 323 darketherDiethyl 3223 2  CHCHClOCHCHCHOCHCHCH Cl   )etherethyl Dichlorodi-,( 33 darketherDiethyl 3223 2     HCHClOCHClCCHCHOCHCHCH Cl HClClOCClCClHOCHC Cl 1010 )etheriethyl Perchlorod( 5252 light 25252 2   (ii) Burning : Ethers are highly inflammable. They burn like alkanes. OHCOOHCOHC 2225252 546  (2) Reaction due to ethernal oxygen (i) Peroxide formation :  : .. .. .. .. 5252 OHCOHC OOHC 252 )( . (a) The boiling point of peroxide is higher than that of ether. It is left as residue in the distillation of ether and may cause explosion. Therefore ether may never be evaporated to dryness. (b) Absolute ether can be prepared by distillation of ordinary ether from conc. 42SOH and subsequent storing over metallic sodium.  Formation of peroxide can be prevented by adding small amount of OCu 2 to ether.  With strong oxidising agent like acid, dichromate ethers are oxidised to aldehydes. OHCHOCHCHOCHCHCH O 2 deAcetaldehy 3 ][2 3223 2    The presence of peroxide can be indicated by the formation of blood red colour complex in the following reaction. )6 to1( colour red Blood 332 ])([ Peroxide      n n n SCN SCNFeFeFe (ii) Oxidation with K2Cr2O7 / H R R CHOCHR     2 (a) Oxidation of ether can only be possible if any one of the alkyl groups of ether has hydrogen on - carbon. (b) -carbon having two hydrogens converts in carboxylic group and -carbon having only one hydrogen converts into keto group. 32223 CHCHCHOCHCH   COOHCHCHCOOHCH H OCrK    233 / 722 3 3 23 CH CH CHOCHCH  3 || 33 / 722 CH O CCHCOOHCH H OCrK    (iii) Salt formation : Due to lone pair of electrons on oxygen atom. Ether behaves as Lewis base and form stable oxonium salt with strong inorganic acids at low temperature. chloride oxoniumDiethy l | 2525252 .. )(   Cl H OHCHClHOCHC or  ClHOHC ])[( 252 sulphate hydrogen oxoniumDiethyl 4 | 252425252 .. )(    HSO H OHCSOHHOCHC or  4252 ])[( HSOHOHC The oxonium salts are soluble in acid solution and ethers can be recovered from the oxonium salts by treatment with water. HClOHCCl H OHC OH   etherDiethyl 252 salt Oxonium | 252 )()( 2  The formation of oxonium salt is similar to the formation of ammonium salts from ammonia and acids. Alcohol, Phenol and Ethers 1217  Ether is removed from alkyl halides by shaking with conc. 42SOH .  Ethers can be distinguished from alkanes with the help of this reaction. (iv) Reaction with Lewis acids : Being Lewis bases, ethers form complexes with Lewis acids such as 3BF , 3AlCl , 3FeCl , etc. These complexes are called etherates. (complex) etherate de trifluoriBoron 3 23 23 3 23 23 .... : BFO CHCH CHCH BFO CHCH CHCH  Similarly, diethyl ether reacts with Grignard reagent forming Grignard reagent etherate. etherate reagent Grignard 232 223 223 )( )( )(2 X CHCHO Mg OCHCH R RMgXOCHCH  Due to the formation of the etherate, Grignard reagents dissolve in ether. That is why Grignard reagents are usually prepared in ethers. However, they cannot be prepared in benzene, because benzene has no lone pair of electrons and therefore, cannot form complexes with them. (3) Reaction involving cleavage of carbon- oxygen bond (i) Hydrolysis (a) With dil. 42SOH : ROHOHROR SOH 242 2   Ethanol 522 etherDiethyl 5252 242 OHHCOHHOCHC SOH   (b) With conc. 42SOH : OHHSOHCSOHHOCHC OHHSOHCSOHOHHC HSOHCOHHCSOHHOCHC 2 sulphate hy drogenEthy l 45242 etherDiethy l 5252 24524252 45252425252 22    (ii) Action of hydroiodic acid (a) With cold HI alcoholEthyl 52 iodideEthyl 52 Cold etherDiethyl 5252 OHHCIHCHIHOCHC   (b) With hot HI OHIRRIHIROR 2 heat 2   (iii) Zeisel method : 33 )alc.( RNOAgIAgNORI   The silver iodide thus form can be detected and estimated. This is the basis of Zeisel method for the detection and estimation of alkoxy group in a compound. (iv) Action of PCl5 3 heat 5 2 POClRClPClROR   . There is no reaction in cold. (v) Reaction with acetyl chloride acetateEthyl 523 heatetherDiethyl 5252 chlorideAcetyl 3 2 HCOOCCHHCOHCCOClCH ZnCl   (vi) Reaction with acid anhydride etherDiethyl 5252 anhydrideAcetic 33 HCOHCOCCHOCOCH  acetateEthyl 523 heat 22 HCOOCCH ZnCl   (vii) Dehydration OHCHCHHOCHC C OAl o 222 300 5252 232   (viii) Reaction with carbon mono oxide ionateEthy l prop 5252 atm. 500 150/ etherDiethy l 5252 3 HCOOCHCCOHOCHC CBF o   (ix) Action of bases 32223 CHCHOCHCHHHCiL   52224 HCOiLCHCHCH   (4) Ring substitution in aromatic ethers : Alkoxy group is ortho and para directing and it directs the incoming groups to ortho and para position. It activates the aromatic ring towards electrophilic substitution reaction. III, IV and V show high electron density at ortho and para position. (i) Halogenation : Phenyl alkyl ethers undergo usual halogenation in benzene ring. For example, Bromination of anisole gives ortho and para bromo derivative even in the absence of iron (III) bromide catalyst. Para isomer is obtained in 90% yield. (ii) Friedel craft reaction OC2H5 Phenyl ethyl ether + HBr  OH Phenol + C2H5Br Ethyl bromide OCH3 Br p- Bromoanisole OCH3 B r o- Bromoanisole OCH3 Anisol e 2 2 CS Br  + OCH3 Anisol e +   3 chlorideMethyl 3 AlCl ClCH OCH3 CH3 Para OCH3 CH3 Ortho + .. :OR I .. :O – R II .. +OR  .. III IV .. +OR  .. : .. +OR V