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• Hydroxyl (OH) functional group ( ROH )• Oxygen is sp3 hybridized • Polar molecule why…….? == > (Oxygen have 2 lone pairs)
1.Primary alcohol: Carbon with –OH is bonded to one other carbon.
H H H C– C– OH or CH3CH2 OH or R CH2 OH H H2.Secondary alcohol: Carbon with –OH is bonded to two other carbons. H H H C–--- C– OH or CH3 C H OH or R – CH OH H H C H H CH3 R
3. Tertiary alcohol: Carbon with –OH is bonded to three other carbons. H CH3 R H H C H H C------ C– OH or CH3 C --- OH or R – C -- OH H H C H H CH3 R
4.Aromatic (phenol): -OH is bonded to a benzene ring. OH
CH3 CH
CH3
CH2OH
CH3 C
CH3
CH3
OHOH
CH3 CH
OH
CH2CH3
Primary (1o) Secondary (2o)
Tertiary (3o) Aromatic (phenol)
CH3CH2CH2OH
4-penten-2-ol (old)
pent-4-ene-2-ol (1997 revision of IUPAC rules)
CH2 CHCH2CHCH3
OH
1.Find the longest carbon chain containing the carbon with the -OH group.
2. Drop the -e from the alkane name, add -ol.3. Number the chain, starting from the end
closest to the -OH group.4.Number and name all substituents.
CH3 CH
CH3
CH2OH
CH3 C
CH3
CH3
OH
CH3 CH
OH
CH2CH3
2-methyl-1-propanol
2-methyl-2-propanol
2-butanol
OH
Br CH3
3-bromo-3-methylcyclohexanol
Naming Priority
• Acids• Esters• Aldehydes• Ketones• Alcohols• Amines
• Alkenes• Alkynes• Alkanes• Ethers• Halides
• When -OH is part of a higher priority class of compound, it is named as hydroxy.
• Example:
CH2CH2CH2COOH
OH
4-hydroxybutanoic acid
• Alcohol can be named as alkyl alcohol.
• Useful only for small alkyl groups.
• Examples:
CH3 CH
CH3
CH2OH CH3 CH
OH
CH2CH3
isobutyl alcohol sec-butyl alcohol
Naming Diols
• Two numbers are needed to locate the two -OH groups.
• Use -diol as suffix instead of -ol.
HO OH
1,6-hexanediol
Glycols
• 1, 2 diols (vicinal diols) are called glycols.• Common names for glycols use the name of the
alkene from which they were made.
CH2CH2
OH OH
CH2CH2CH3
OH OH
1,2-ethanediol
ethylene glycol
1,2-propanediol
propylene glycol
• -OH group is assumed to be on carbon 1.• For common names of disubstituted phenols,
use ortho- for 1,2; meta- for 1,3; and para- for 1,4.
• Methyl phenols are cresols.OH
Cl
3-chlorophenol
meta-chlorophenol
OH
H3C
4-methylphenol
para-cresol
1. Boiling point of alcohol
2. Solubility of alcohol
3. Acidity of alcohol
i) Higher compared to corresponding alkane.. Why?
ii) Unusually high boiling points due to hydrogen bonding between molecules
alcohol M.p B.p Density• Methanol -97 65 0.792• Ethanol -114 78 0.789• Propan-1-ol - 126 97 0.804• Propan-2-ol - 88 82 0.786• Butan-1-ol - 90 118 0.810• 2-methylpropan-1-ol -118 108 0.802• Butan-2-ol -114 100 0.808• 2,2-dimethylethanol 25 83 0.789• Pentan-1-ol - 79 138 0.817• Hexan-1-ol - 52 158 0.819
Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases
Solubility decreases as the size of the alkyl group increases.
• pKa range: 15.5-18.0 (water: 15.7)• pKa … ?• Acidity decreases as alkyl group
increases.• Halogens increase the acidity.• Phenol is 100 million times more acidic
than cyclohexanol!
Table of Ka Values
CH3 OH
React methanol and ethanol with sodium metal (redox reaction).
CH3CH2OH + Na CH3CH2O Na + 1/2 H2
React less acidic alcohols with more reactive potassium.
+ K (CH3)3CO K + 1/2 H2)3C OH(CH3
1. Manufactured preparation of alcohol
2. Lab preparation of alcohol
i) Grignard reagents
ii ) Reduction of aldehyde/ketones
iii) Hydrolysis of alkyl halide
iv) Hydration of alkenes
Preparation of Methanol :
By passing (execess) hydrogen and carbon monoxide over chromium (III) oxide/Zinc Oxide as catalyst at 350- 400o C
Cr2O3/ZnO cat
2H2 + CO ============ > CH3OH
350-400 oC high preesure
• Preparation of Ethanol :
• By direct hydrolysis of ethylene.
• Mixture of C2H4 and water vapour passed over phosphoric acid 300oC 68-70 atm pressure
phosphoric acid
• C2H4 + H2O ======== > CH3CH2OH
• 300 oC 68-70 atm
• Fermentation:
• Diastase
• 2(C6H10O5)n + nH2O == > n C12H22O11
• 60 o C maltose• Maltase
• C12H22O11 + H2O === > C6H12O6
Glucose
Zymase
• C6H12O6 === > 2CH3CH2OH + 2CO2
• ethanol
1. Grignard Reaction (RMgX) H ether H H2O H
C=O + RMgMX == > H C–OMgX ==> H C OH + MgXOH
H R dil acid R
Formaldehyde 1o alcohol
R1 ether H H
C=O + RMgMX == > R1 C–OMgX ==> R1 C OH + MgXOH
H R R
Acetaldehyde 2o Aocohol
Grignard + formaldehyde yields a primary alcohol with one additional carbon.
C OH
HC
CH3
H3C CH2 C MgBr
H
HH
CH3 CH
CH3
CH2 CH2 C
H
H
O MgBr
HOHCH3 CH
CH3
CH2 CH2 C
H
H
O H
Grignard + aldehyde yields a secondary alcohol.
MgBrCH3 CH
CH3
CH2 CH2 C
CH3
H
OC
CH3
H3C CH2 C MgBr
H
HH
C OH
H3C
CH3 CH
CH3
CH2 CH2 C
CH3
H
O HHOH
R2 ether R2 R2
C=O + RMgMX == > R1 C–OMgX ==> R1 C OH + MgXOH
R1 R R
Acetone 3o Aocohol
Grignard Reaction (RMgX)
Grignard + ketone yields a tertiary alcohol.
MgBrCH3 CH
CH3
CH2 CH2 C
CH3
CH3
OC
CH3
H3C CH2 C MgBr
H
HH
C OH3C
H3C
CH3 CH
CH3
CH2 CH2 C
CH3
CH3
O HHOH
Some Grignard ReagentsBr
+ Mgether MgBr
CH3CHCH2CH3
Clether
+ Mg CH3CHCH2CH3
MgCl
CH3C CH2
Br + Mgether
CH3C CH2
MgBr
R1 LiAlH4
C=O == == > R1 CH2OH
H Ether
Acetaldehyde 1o Aocohol
R1 LiAlH4
C=O == == > R1 CHOH
R Ether R
Aacetone 2o Aocohol
Since LiALH4 is strong reduction agent, other reduction agent such as:
LiBH4 ( in Ether )
NaBH4(In Ethanol/H2O)
Also can be used.
Comparison of Reducing Agents
• LiAlH4 is stronger.
• LiAlH4 reduces more stable compounds which are resistant to reduction.
1. Hydrolysis (substitution) of OH- on alkyl halide
CH3CH2X + HOH ===>CH3CH2OH + HX
• 2.Hydration of alkenes
H2C=CH2 + H2O == > CH3CH2OH
1. Dehydration to alkene2. Oxidation to aldehyde, ketone3. Substitution to form alkyl halide4. Reduction to alkane5. Esterification6. Williamson synthesis of ether
1. Conc. H2SO4 produces alkene
2. Carbocation intermediate
3. Saytzeff product
4. Bimolecular dehydration produces ether
5. Reaction condition:
Low temp, 140°C and below, favors ether
High temp, 180°C and above, favors alkene
CH3CHCH3
OHH2SO4
alcoholCH3CHCH3
OH
H
CH3CHCH3
CH2 CHCH3H2O
CH3OH
H3O+
CH3OH CH3 OH2 CH3 O
H
CH3
H2OCH3OCH3
• 1° alcohol to aldehyde to carboxylic acid• Difficult to stop at aldehyde• Use pyridinium chlorochromate (PCC) to limit the
oxidation.• PCC can also be used to oxidize 2° alcohols to
ketones.
CH3CH2CH2CH2
OH N H CrO3Cl
CH3CH2CH2CH
O
CH3CHCH2CH3
OHNa2Cr2O7 / H2SO4
CH3CCH2CH3
O
=>
1. 2° alcohol becomes a ketone2. Reagent is Na2Cr2O7/H2SO4
3. Active reagent probably H2CrO4
4. Color change: orange to greenish-blue
Example
• Cannot lose 2 H’s
• Basis for chromic acid test
=>
• Collins reagent: Cr2O3 in pyridine
• Jones reagent: chromic acid in acetone
• KMnO4 (strong oxidizer)
• Con. Nitric acid (strong oxidizer)
• CuO, 300°C (industrial dehydrogenation). =>
• Dehydrate with conc. H2SO4, then add H2
• Tosylate, then reduce with LiAlH4
CH3CHCH3
OHH2SO4
CH2 CHCH3H2
PtCH3CH2CH3
alcohol alkene alkane
alcohol
CH3CHCH3
OHTsCl
CH3CHCH3
OTsLiAlH4
alkane
CH3CH2CH3
tosylate
=>
• -OH of alcohol is protonated
• -OH2+ is good leaving group
• 3° and 2° alcohols react with Br- via SN1
• 1° alcohols react via SN2
H3O+
Br-
R O H R O H
H
R Br =>
• Chloride is a weaker nucleophile than bromide.
• Add ZnCl2, which bonds strongly with -OH, to promote the reaction.
• The chloride product is insoluble.
• Lucas test: ZnCl2 in conc. HCl– 1° alcohols react slowly or not at all.– 2 alcohols react in 1-5 minutes.– 3 alcohols react in less than 1 minute.
• HI does not react• Poor yields of 1° and 2° chlorides• May get alkene instead of alkyl halide• Carbocation intermediate may rearrange.
• Good yields with 1° and 2° alcohols
• PCl3 for alkyl chloride (but SOCl2 better)
• PBr3 for alkyl bromide
• P and I2 for alkyl iodide (PI3 not stable)
=>
• P bonds to -OH as Br- leaves
• Br- attacks backside (SN2)
• HOPBr2 leaves
• Produces alkyl chloride, SO2, HCl
• S bonds to -OH, Cl- leaves
• Cl- abstracts H+ from OH
• C-O bond breaks as Cl- transferred to C
• Fischer: alcohol + carboxylic acid
• Tosylate esters
• Sulfate esters
• Nitrate esters
• Phosphate esters
Can be carried out by following methods
• Acid + Alcohol yields Ester + Water
• Sulfuric acid is a catalyst.
• Each step is reversible.
CH3 C OH
O
+ CH2CH2CHCH3
CH3
OHH
+
CH3C
O
OCH2CH2CHCH3
CH3
+ HOH
Sulfate Esters
Alcohol + Sulfuric Acid
+HO S
O
O
OH H O CH2CH3H
+
OCH2CH3
O
O
SHO
CH3CH2O H + OCH2CH3
O
O
SHOH
+
CH3CH2O S
O
O
OCH2CH3
Nitrate Esters
+ H O CH2CH3H
+
N OH
O
OOCH2CH3N
O
O
CH2
CH2
CH2
O H
O H
O H
+ 3 HO NO2
CH2
CH2
CH2
O NO2
O NO2
O NO2
nitroglycerineglycerine =>
Phosphate Esters
P
O
OH
OH
HOCH3OH
P
O
OH
OH
CH3OCH3OH
P
O
OCH3
OH
CH3O
P
O
OCH3
OCH3
CH3O
CH3OH
=>
• ROH + Na (or NaH) yields sodium alkoxide• RO- + 1° alkyl halide yields ether (Williamson
ether synthesis)
CH3CH2CHCH3
O
CH3CH2 Br+ CH2CH2CH
CH3
O CH2CH3
=>
Acid Catalyst
CH3-CH2 OH == > CH2=CH2+ H2O Acid Catalyst
• CH3CH –CH2 == > CH3CH2=CH2 + H2O
H OH
1. Solvent
2. Sources of other materials
=>
C2H5OH
R-COOC2H5 C2H5NH2
Starh, Sugar, Cellulose C2H5Cl
C2H4
C2H5HSO4
C2H5OC2H5
CHI3C2H5ONa CH3COOH
CH3CHOZn +Acid / LiAlH4 (reduction)
Boil with
KOH
SOl 2, P
Cl 5 or H
Cl
Excess acid K2 Cr
2 O7 (Oxidation)
Yeast
(Fer
men
tatio
n)H
NO
2
I 2 +
Na 2
CO
3 so
ln
Iodo
form
test
c H 2SO 4 (l
ow temp )
Exces
s Alco
hol +
con
H 2SO 4
140
o C
Warm with
H 2O
RCOOH Esterification
Heat with KOH soln
(hydrolysis)
Vapour + Air (Ag at 600 o C) (Oxid )
Preparation Substitution Reaction
He
at
with
C2H
5O
H
c H
2SO
4
He
at
17
0o C
– H
2O
Na
dil acids LiAlH
4 (reduction) - H
2O
Methanol• “Wood alcohol”
• Industrial production from synthesis gas
• Common industrial solvent
• Fuel at Indianapolis 500– Fire can be extinguished with water– High octane rating– Low emissions– But, lower energy content– Invisible flame =>
Ethanol
• Fermentation of sugar and starches in grains• 12-15% alcohol, then yeast cells die.• Distillation produces “hard” liquors• Azeotrope: 95% ethanol, constant boiling• Denatured alcohol used as solvent• Gasahol: 10% ethanol in gasoline• Toxic dose: 200 mL ethanol, 100 mL methanol
=>
2-Propanol
• “Rubbing alcohol”
• Catalytic hydration of propene
=>
CH2 CH CH2 H2O100-300 atm, 300°C
catalyst+ CH3 CH
OH
CH3
Formation of Phenoxide Ion
Phenol reacts with hydroxide ions to form phenoxide ions - no redox is necessary.
O H
+ OH
O
+ HOH
pKa = 10pKa = 15.7
=>
Glycols (Review)
• Syn hydroxylation of alkenes– osmium tetroxide, hydrogen peroxide– cold, dilute, basic potassium permanganate
• Anti hydroxylation of alkenes– peroxyacids, hydrolysis
Organometallic Reagents
• Carbon is bonded to a metal (Mg or Li).
• Carbon is nucleophilic (partially negative).
• It will attack a partially positive carbon.– C - X– C = O
• A new carbon-carbon bond forms. =>
Organolithium Reagents
• Formula R-Li (reacts like R:- +Li)
• Can be produced from alkyl, vinyl, or aryl halides, just like Grignard reagents.
• Ether not necessary, wide variety of solvents can be used.
=>
Reaction with Carbonyl
• R:- attacks the partially positive carbon in the carbonyl.
• The intermediate is an alkoxide ion.• Addition of water or dilute acid protonates the
alkoxide to produce an alcohol.
RC O R C O
HOHR C OH
OH=>
How would you synthesize…
CH3CH2CHCH2CH2CH3
OH CH2OH
OH
CH3C
OH
CH2CH3
CH3 =>
Grignard and Ester (1)
• Grignard attacks the carbonyl.
• Alkoxide ion leaves! ? !
C OCH3O
H3C
MgBrR MgBr C
CH3
OCH3
OR
C
CH3
OCH3
OR MgBr C
CH3
RO
+ MgBrOCH3
Ketone intermediate =>
Second step of reaction
• Second mole of Grignard reacts with the ketone intermediate to form an alkoxide ion.
• Alkoxide ion is protonated with dilute acid.
C
CH3
RO
R MgBr + C
CH3
R
OR MgBr
HOH
C
CH3
R
OHR
=>
How would you synthesize...
CH3CH2CCH3
OH
CH3
C
OH
CH3
Using an acid chloride or ester.
CH3CH2CHCH2CH3
OH
=>
Grignard Reagent + Ethylene Oxide
• Epoxides are unusually reactive ethers.
• Product is a 1º alcohol with 2 additional carbons.
MgBr + CH2 CH2
OCH2CH2
O MgBr
HOH
CH2CH2
O H
=>
Limitations of Grignard
• No water or other acidic protons like O-H, N-H, S-H, or -C—C-H. Grignard reagent is destroyed, becomes an alkane.
• No other electrophilic multiple bonds, like C=N, C—N, S=O, or N=O.
=>
Reduction of Carbonyl
• Reduction of aldehyde yields 1º alcohol.• Reduction of ketone yields 2º alcohol.• Reagents:
– Sodium borohydride, NaBH4
– Lithium aluminum hydride, LiAlH4
– Raney nickel
=>
Sodium Borohydride
• Hydride ion, H-, attacks the carbonyl carbon, forming an alkoxide ion.
• Then the alkoxide ion is protonated by dilute acid.
• Only reacts with carbonyl of aldehyde or ketone, not with carbonyls of esters or carboxylic acids.
HC
O
HC
H
OHC
H
OH HH3O+
=>
Lithium Aluminum Hydride
• Stronger reducing agent than sodium borohydride, but dangerous to work with.
• Converts esters and acids to 1º alcohols.
CO
OCH3C
OH H
HH3O+
LAH =>
Catalytic Hydrogenation
• Add H2 with Raney nickel catalyst.
• Also reduces any C=C bonds.
O
H2, Raney Ni
OH
NaBH4
OH
=>
Thiols (Mercaptans)
• Sulfur analogues of alcohols, -SH.
• Named by adding -thiol to alkane name.
• The -SH group is called mercapto.
• Complex with heavy metals: Hg, As, Au.
• More acidic than alcohols, react with NaOH to form thiolate ion.
• Stinks! =>
Thiol Synthesis
Use a large excess of sodium hydrosulfide with unhindered alkyl halide to prevent dialkylation to R-S-R.
H S_
R X R SH +_
X
=>
Thiol Oxidation
• Easily oxidized to disulfides, an important feature of protein structure.
R SH + RHSBr2
Zn, HClR S S R + 2 HBr
• Vigorous oxidation with KMnO4, HNO3, or NaOCl, produces sulfonic acids.
SHHNO3
boilS
O
O
OH
=>
Biological Oxidation
• Catalyzed by ADH, alcohol dehydrogenase.• Oxidizing agent is NAD+, nicotinamide
adenine dinucleotide.• Ethanol oxidizes to acetaldehyde, then acetic
acid, a normal metabolite.• Methanol oxidizes to formaldehyde, then
formic acid, more toxic than methanol.• Ethylene glycol oxidizes to oxalic acid, toxic.• Treatment for poisoning is excess ethanol.
=>
Unique Reactions of Diols
• Pinacol rearrangement• Periodic acid cleavage
=>
Pinacol Rearrangement• Pinacol: 2,3-dimethyl-2,3-butanediol
• Dehydration with sulfuric acid
CH3 C
CH3
OH OH
CH3
C CH3H
+
CH3 C
CH3
OH OH
CH3
C CH3
H
CH3 C
CH3
OH
CCH3
CH3
CH3 C
CH3
OH
CCH3
CH3CH3 C
OH
CH3
C CH3
CH3
CH3 C
OH
CH3
C CH3
CH3
CH3 C
O
CH3
C CH3
CH3
pinacolone
=>
Periodic Cleavage of Glycols
Same products formed as from ozonolysis of the corresponding alkene.
CH3 C
H
OH OH
CH3
C CH3
HIO4CH3 C
H
O+ C
OCH3
CH3
C CH3C
H CH3
CH3
OsO4
H2O2
O3
(CH3)2S
=>
Oxidation States
• Reagents used:
CrO42- reduced to Cr2O3
KMnO4 reduced to MnO2
• Oxidation: loss of H2, gain of O, O2, or X2
• Reduction: gain of H2 or H-, loss of O, O2, or X2
• Neither: gain or loss of H+, H2O, HX =>