Transcript Alcohols

‫‪Alcohols‬‬
‫‪Nomenclature of alcohols:‬‬
‫‪IUPAC system‬‬
‫نذكر اسم ‪ alkane‬و نحذف منه حرف ‪ e‬و نستبدله ب ‪ol‬‬
‫و في حالة الترقيم نعد من الطرف الذي يعطى مجموعة ‪ OH‬أقل ترقيم‬
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‫‪‬‬
‫في حالة ‪ alkene or alkyne‬نحذف حرف ‪ e‬و نستبدله ب ‪ol‬‬
‫و في حالة الترقيم نعد من الطرف الذي يعطى مجموعة ‪ OH‬أقل ترقيم‬
‫‪Examples‬‬
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Common names
alcohol ‫ ثم نكتب كلمة‬OH ‫المتصلة ب‬alkyl ‫نذكر اسم‬
Examples
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‫‪Carbinol method‬‬
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‫تعتمد هذه الطريقة على أن ‪ CH3OH‬يسمى ب ‪ Carbinol‬و تسمى‬
‫‪ alcohols‬كمشتقات منه بذكر أسماء ‪ alkyl‬المستبدلة بدال من ذرات‬
‫الهيدروجين في مجموعة ‪ CH3‬ثم نكتب كلمة ‪Carbinol‬‬
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‫‪Examples‬‬
Examples of nomenclature
IUPAC name
2-propen-1-ol
2-Butanol
2-Methyl-1-Propanol
Common name
Allyl alcohol
Sec-Butyl alc.
Isobutyl alc.
Ethyl methyl
carbinol
Isopropyl carbinol
Carbinol method Vinyl carbinol
Classification of alcohols
According to number of OH groups
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Monohydroxy alcohols: which contain one OH group e.g.
ethanol
Dihydroxy alcohols: which contain two OH group e.g.
ethyleneglycol.
Polyhydroxy alcohols: which contain more than two OH groups
e.g. glycerol and carbohydrate.
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According to number of OH groups
Monohydroxy alcohols are classified according to type of
carbon bearing OH into three types:
• 1ry alcohols: in which OH attach with 1ry carbon e.g.
RCH2OH
• 2nd alcohols: in which OH attach with 2nd carbon e.g. R2CHOH
• t-alcohols : in which OH attach with tertiary carbon e.g.
R3COH
Preparation of alcohols
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a) Preparation of 1ry alcohol1.
1- Hydrolysis of alkene
2. Hydrolysis of alkyl halide
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E.g. conversion of benzene to benzyl alcohol
3. Reduction of carbonyl compound
Reduction of aldehyde gives 1ry alcohol, while of ketone
gives 2nd alcohol
NaBH4 reduce C=O and not reduce C=C
e.g.
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CH3CH=CH-CHO + NaBH4 CH3CH=CH-CH2OH
Crotonaldehyde
2-Butenol
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4. Reduction of acids and esters
Acids and esters are reduced to 1ry alcohol by use of LiAlH4
E.g. CH3COOH + LiAlH4
CH3COOCH2CH3 + LiAlH4
CH3CH2OH
2 CH3CH2OH
Also Na/ROH can reduce esters to 1ry alcohol
Grignard reagent can be prepared as follow:
Grignard reagent is used to prepare 1ry, 2nd, and t-alcohols
a) Preparation of 1ry alcohol
1ry alcohol is prepared from Grignard reagent and formaldehyde
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b) Preparation of secondary alcohols
Secondary alcohols are prepared from Grignard reagent and
aldehyde other than formaldehyde.
c) Preparation of tertiary alcohols
Tertiary alcohols are prepared from Grignard reagent and ketones.
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Grignard reagent is used to synthesis many organic
compounds e.g.
Reactions of alcohols
1)Replacement of OH by halogen
a) By reaction with HX
ROH + HX
RX + H2O
X= I, Br and Cl
e.g. CH3CH2OH + HBr
CH3CH2Br +HOH
b) By reaction with phosphorus halide
R OH
R OH
3 R OH
PCl5
Cl
R
Cl + HCl + SO2
SOCl2
PCl3
+ HCl + POCl3
R
3R
Cl
+ H3PO3
Dehydration of alcohols
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See alkene
Formation of esters
e.g. CH3CH2OH + CH3COOH
Ethanol
CH3COOCH2CH3 + H2O
acetic acid
Ethyl acetate
Differentiation between different types of alcohols
1. By oxidation
a) 1ry alcohol oxidize to give aldehyde or acid
[O]
RCH2OH
e.g.
CH3CH2CH2OH
propan-1-ol
RCHO
aldehyde
[O]
[O]
RCOOH
acid
CH3CH2CHO
propionaldehyde
[O]
CH3CH2COOH
propionic acid
Examples of oxidizing agent are K2Cr2O7/ H2SO4, KMnO4 and
Cu/250oC
b)2nd alcohol oxidize to give ketone
c) Tertiary alcohols do not oxidize
Iodoform test
This reaction occurs with alcohols containing
Also aldehydes or ketones containing CH3-CO can give iodoform
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Examples of iodoform equations
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Mechanism of iodoform
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(a) For alcohols
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(b) For aldehyde and ketones
Only one aldehyde can give iodoform, this aldehyde is
acetaldehyde, the mechanism of aldehyde and ketones are
step 2, and 3 in alcohol.
E.g. acetone
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Ethers
Nomenclature of ethers
IUPAC nomenclature
‫ فرع في سلسلة االلكان‬RO ‫ و تتم التسمية باعتبار‬Alkoxy ‫ ب‬RO ‫تسمى‬
E.g.
CH3OMethoxy
CH3CH2OEthoxy
CH3CH2CH2CH2OButoxy
Examples of ethers
CH3OCH2CH2CH3
1-Methoxypropane
CH3CH2OCH2CH3
Ethoxyethane
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Comman Nomenclature
ether ‫نذكر أسماء األلكيل المتصلة بذرة األوكسجين ثم نكتب كلمة‬
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Examples
CH3CH2OCH2CH3 C6H5OCH3
(CH3) 3 C-OCH2CH3
Diethyl ether
methyl phenyl ether
t-Butyl ethyl
ether
(Anisole)
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Preparation of ethers
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From alcohols
Wiliamson synthesis
It is reaction between alkoside and alkyl halide
E.g. preparation of diethyl ether
Question
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Show how could you prepare the following ethers:
(a) Anisole (phenyl methyl ether)
Answer
(b) t- butyl ethyl et
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Observation:
Alkyl halide must be primary or secondary because t-alkyl halide
undergoes loss of HCl (elimination) so it gives alkene not ether e.g.
Reaction of ethers
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Reaction with acid halide
‫‪Cyclic ethers‬‬
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‫تسمى ‪ Cyclic ethers‬ب ‪ alkene oxide‬أو نحدد رقمي ذرتي الكربون‬
‫المتصلتين بذرة األوكسجين و يسميا ب ‪ epoxy‬و ينسبا ل ‪alkane‬‬
Preparation of cyclic ethers
In case of unsymmetrical cyclic ethers, the product
depends on the reaction condition
In case of acidic medium, nucleophile goes to more steric
carbon i.e. carbon containing less number of hydrogen.
In case of basic medium, nucleophile goes to less steric
carbon i.e. carbon containing great number of hydrogen.
Examples