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Chapter 10: Chapter 10: Structure and Synthesis of Structure and Synthesis of Alcohols Alcohols 100

Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

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Page 1: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Chapter 10: Chapter 10: Structure and Synthesis of Structure and Synthesis of

AlcoholsAlcoholsAlcoholsAlcohols

100

Page 2: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Physical Properties

Alcohols can be:CH3 CH

OH

CH2CH3*

CH3 CH

CH3

CH2OH*

Secondary alcohol

101

CH3 C

CH3

CH3

OH*

*Primary alcohol

Secondary alcohol

Tertiary alcohol

Page 3: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

• Most alcohols (C1-C12) are liquids at room temperature• Bp much higher than alkanes of similar molecular weights (H-bonding)

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Page 4: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

� Acidity: the H of the hydroxyl group is weakly acidic:

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Page 5: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

� This hydroxyl proton can be removed with suitable bases. Bases such as KOH or NaOH are not strong enough. NaH, KH or Na(s), K(s) are usually used.

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Page 6: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

� In the case of phenols, the pKa of the hydroxyl group is around 10 and weaker bases can be used (NaOH, KOH, etc…)

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Page 7: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Synthesis of AlcoholsSynthesis of Alcohols(Review)(Review)

§ Hydration(a) Direct (8.4)

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Page 8: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Mechanism of Direct Hydration of Mechanism of Direct Hydration of AlkenesAlkenes

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Page 9: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

(b) Indirect (4.8)(1) Oxymercuration/Demercuration (8.5)

(2) Hydroboration/Oxidation (8.7)

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Page 10: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

§ Hydroxylation (8.14)

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Page 11: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

New Synthesis of Alcohols(Nu attack on carbonyl compounds)

An excellent method to make alcohols. Depending on the type of carbonyl used, primary, secondary and tertiary alcohols are all available from this reaction.available from this reaction.

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Page 12: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

2 types of reagents can deliver nucleophilic carbons to C=O:

◦ Grignard reagent: R-Mg-X◦ Alkyl Lithium: R-Li

R MgX

δ− δ+

R Li

δ+δ−

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Page 13: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

§ Synthesis of Grignard Reagents (10.8)

BrMgBr

112

Br

+ Mgether MgBr

CH3CHCH2CH3

Clether

+ Mg CH3CHCH2CH3

MgCl

Page 14: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

� Alkyl Lithium can be prepared in a similar way:

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Page 15: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

§ Synthesis of 1oAlcohols (10.9)Grignards or alkyl lithium react with formaldehyde to produce primary alcohols. The carbon chain increases by one carbon from the original organometallic reagent.

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Page 16: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

§ Synthesis of 2oAlcohols (10.9)other aldehydes react to give secondary alcohols with either Grignard reagents or alkyl lithiums to produce secondary alcohols

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Page 17: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

§ Synthesis of 3oAlcohols (10.9)reaction of ketones with RLi or RMgX will produce tertiary alcohols

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Page 18: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

§ 3oAlcohols by Acyl Substitution(10.9)acid chlorides and esters react with either Grignard reagents or alkyl lithiums via the acyl substitution mechanism. Since the resulting product is a ketone, the reaction will continue and eventually produce the corresponding tertiary eventually produce the corresponding tertiary alcohol.

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Page 19: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Mechanism of Acyl SubstitutionMechanism of Acyl SubstitutionIn the presence of a Grignard or alkyl lithium the reaction will first produce a ketone which will continue to react to produce the corresponding 3o alcohol.

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Page 20: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

� Here is an example of this reaction using two equivalent of grignard reagent with an ester.

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Page 21: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

1oAlcohols With 2 Extra Carbons on the Alkyl Chain. (10.9)

These compounds are generated by the reaction of RLi or RMgX with epoxides.◦ Epoxides are electrophilic due to the ring strain.◦ 2 extra carbons will be added to the alkyl chain.

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Page 22: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Limitations of Grignard ReagentsLimitations of Grignard Reagents� Grignards are good nucleophiles but in the presence of acidic protons it will acts as a strong base. ◦ No water or other acidic protons like ◦ No water or other acidic protons like O—H, N—H, S—H, or terminal alkynes.

� No other electrophilic multiple bonds, like C═N, C≡≡≡≡N, S═O, or N═O.

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Page 23: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Practice QuestionPractice Question� What is the major organic product of the following reactions. Disregard stereoisomers.

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Page 24: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

� 3-Methyl-3-hexanol can be prepared from the reaction of 2-pentanone and ethylmagnesium bromide as shown below. What other combination or grignards and ketones can be used to prepare this compound?

2) H3O+

1) CH3CH2MgBrO

OH

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Page 25: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Reduction of Carbonyl CompoundsReduction of Carbonyl Compounds (10.11)(10.11)

� Reduction of the carbonyl group also produces alcohol by nucleophilic attack to the carbon of the carbonyl. In this case the nucleophile is the hydride ion. Protonation of the resulting alkoxide ion gives the alcohol.

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Page 26: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

2 common reagents to carry out this transformation are :

LiAlH4 : lithium aluminum hydride

NaBH4 : sodium borohydride

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Page 27: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

NaBH4 is selective only for ketones, aldehydes and acid chlorides. LiAlH4 will reduce all carbonyl compounds.

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Page 28: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

� This selectivity can be used in synthesis to control which functional group reacts.

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Page 29: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Mechanism of Hydride Reduction of CarbonylsMechanism of Hydride Reduction of Carbonyls(Ketones and Aldehydes)(Ketones and Aldehydes)

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Page 30: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Mechanism of Acid Chloride/Ester ReductionMechanism of Acid Chloride/Ester Reduction

� In the case of esters and acid chlorides, two equivalents of the hydride are transferred since the first product is a ketone. 1o alcohols are produced.

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Page 31: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Catalytic HydrogenationCatalytic Hydrogenation (10.11)(10.11)

� Similar to the hydrogenation of alkene seen in CHEM201, addition of H2 to the carbonyl of ketones and aldehydes is possible resulting in the formation of alcohols.alcohols.

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Page 32: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

� This reaction is also complementary to the reduction using metal hydrides as it allow for other reduction to take place.

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Page 33: Chapter 10: Structure and Synthesis of Alcohols 10: Structure and Synthesis of Alcohols 100. Physical Properties Alcohols can be: CH3 CH OH CH2CH3 * CH3 CH CH3 ... Practice Questions

Practice QuestionsPractice Questions� Complete the following reactions.

NaBH4

132

COOCH3

NaBH4

MeOH