CHE-302 Review
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CHE-302 Review. Nomenclature Syntheses Reactions Mechanisms Spectroscopy. Aromatic Hydrocarbons (Electrophilic Aromatic Substitution) Spectroscopy (infrared & H-nmr) Arenes Aldehydes & Ketones Carboxylic Acids Functional Derivatives of Carboxylic Acids

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Che 302 review

CHE-302 Review


Che 302 review

Nomenclature

Syntheses

Reactions

Mechanisms

Spectroscopy


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Aromatic Hydrocarbons (Electrophilic Aromatic Substitution)

Spectroscopy (infrared & H-nmr)

Arenes

Aldehydes & Ketones

Carboxylic Acids

Functional Derivatives of Carboxylic Acids

Acid Chlorides, Anhydrides, Amides, Esters

Carbanions

Amines & Diazonium Salts

Phenols


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Mechanisms:

Electrophilic Aromatic Substitution

Nitration

Sulfonation

Halogenation

Friedel-Crafts Alkylation & Acylation

Nucleophilic Addition to Carbonyl

Nucleophilic Addition to Carbonyl, Acid Catalyzed

Nucleophilic Acyl Substitution

Nucleophilic Acyl Substitution, Acid Catalyzed


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Aromatic Hydrocarbons

hydrocarbons

aliphaticaromatic

alkanesalkenesalkynes


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Aliphatic compounds: open-chain compounds and ring compounds that are chemically similar to open-chain compounds. Alkanes, alkenes, alkynes, dienes, alicyclics, etc.

Aromatic compounds: unsaturated ring compounds that are far more stable than they should be and resist the addition reactions typical of unsaturated aliphatic compounds. Benzene and related compounds.


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Nomenclature for benzene:

monosubstituted benzenes:

Special names:


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  • Electrophilic Aromatic Substitution (Aromatic compounds)

  • Ar-H = aromatic compound

  • 1. Nitration

  • Ar-H + HNO3, H2SO4 Ar-NO2 + H2O

  • Sulfonation

  • Ar-H + H2SO4, SO3 Ar-SO3H + H2O

  • Halogenation

  • Ar-H + X2, Fe  Ar-X + HX

  • Friedel-Crafts alkylation

  • Ar-H + R-X, AlCl3 Ar-R + HX


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  • Friedel-Crafts alkylation (variations)

  • Ar-H + R-X, AlCl3 Ar-R + HX

  • Ar-H + R-OH, H+ Ar-R + H2O

  • c) Ar-H + Alkene, H+ Ar-R


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Common substituent groups and their effect on EAS:

-NH2, -NHR, -NR2

-OH

-OR

-NHCOCH3

-C6H5

-R

-H

-X

-CHO, -COR

-SO3H

-COOH, -COOR

-CN

-NR3+

-NO2

ortho/para directors

increasing reactivity

meta directors


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  • If there is more than one group on the benzene ring:

  • The group that is more activating (higher on “the list”) will direct the next substitution.

  • You will get little or no substitution between groups that are meta- to each other.


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“Generic” Electrophilic Aromatic Substitution mechanism:


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Mechanism for nitration:


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Mechanism for sulfonation:


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Mechanism for halogenation:


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Mechanism for Friedel-Crafts alkylation:


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Mechanism for Friedel-Crafts with an alcohol & acid


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Mechanism for Friedel-Crafts with alkene & acid:

electrophile in Friedel-Crafts alkylation = carbocation


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Arenes

alkylbenzenes

alkenylbenzenes

alkynylbenzenes

etc.


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Alkylbenzenes, nomenclature:

Special names


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others named as “alkylbenzenes”:


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Use of phenylC6H5- = “phenyl”

do not confuse phenyl (C6H5-) with benzyl (C6H5CH2-)


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Alkenylbenzenes, nomenclature:


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  • Alkylbenzenes, syntheses:

  • Friedel-Crafts alkylation

  • Modification of a side chain:

  • a) addition of hydrogen to an alkene

  • b) reduction of an alkylhalide

  • i) hydrolysis of Grignard reagent

  • ii) active metal and acid

  • c) Corey-House synthesis


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Alkynylbenzenes, nomenclature:


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Friedel-Crafts alkylation


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  • Friedel-Crafts limitations:

  • Polyalkylation

  • Possible rearrangement

  • R-X cannot be Ar-X

  • NR when the benzene ring is less reactive than bromobenzene

  • NR with -NH2, -NHR, -NR2 groups


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Modification of side chain:


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  • Alkylbenzenes, reactions:

  • Reduction

  • Oxidation

  • EAS

  • a) nitration

  • b) sulfonation

  • c) halogenation

  • d) Friedel-Crafts alkylation

  • Side chain

  • free radical halogenation


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Alkylbenzenes, EAS

-R is electron releasing. Activates to EAS and directs ortho/para


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Alkylbenzenes, free radical halogenation in side chain:

Benzyl free radical


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  • Alkenylbenzenes, syntheses:

  • Modification of side chain:

  • a) dehydrohalogenation of alkyl halide

  • b) dehydration of alcohol

  • c) dehalogenation of vicinal dihalide

  • d) reduction of alkyne

  • (2. Friedel-Crafts alkylation)


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Alkenylbenzenes, synthesis modification of side chain


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  • Alkenylbenzenes, reactions:

  • Reduction

  • Oxidation

  • EAS

  • Side chain

  • a) add’n of H2j) oxymercuration

  • b) add’n of X2k) hydroboration

  • c) add’n of HXl) addition of free rad.

  • d) add’n of H2SO4m) add’n of carbenes

  • e) add’n of H2On) epoxidation

  • f) add’n of X2 & H2Oo) hydroxylation

  • g) dimerizationp) allylic halogenation

  • h) alkylationq) ozonolysis

  • i) dimerizationr) vigorous oxidation


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Alkenylbenzenes, reactions: reduction


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Alkenylbenzenes, reactionsoxidation


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Alkenylbenzenes, reactionsEAS?


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100 syn-oxidation; make a model!


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Alkynylbenzenes, syntheses:

Dehydrohalogenation of vicinal dihalides


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  • Alkynylbenzenes, reactions:

  • Reduction

  • Oxidation

  • EAS

  • Side chain

  • a) reductione) as acids

  • b) add’n of X2f) with Ag+

  • c) add’n of HXg) oxidation

  • d) add’n of H2O, H+


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Alkynylbenzenes, reactions: reduction

Anti-

Syn-


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Alkynylbenzenes, reactions: oxidation


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Alkynylbenzenes, reactionsEAS?


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Alkynylbenzenes, reactions: side chain:


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Aldehydes and Ketones


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Nomenclature:

Aldehydes, common names:

Derived from the common names of carboxylic acids;

drop –ic acid suffix and add –aldehyde.

CH3

CH3CH2CH2CH=O CH3CHCH=O

butyraldehyde isobutyraldehyde

(α-methylpropionaldehyde)


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Aldehydes, IUPAC nomenclature:

Parent chain = longest continuous carbon chain containing the carbonyl group; alkane, drop –e, add –al. (note: no locant, -CH=O is carbon #1.)

CH3

CH3CH2CH2CH=O CH3CHCH=O

butanal 2-methylpropanal

H2C=OCH3CH=O

methanalethanal


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Ketones, common names:

Special name:acetone

“alkyl alkyl ketone” or “dialkyl ketone”


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(o)phenones:

Derived from common name of carboxylic acid, drop –ic acid, add –(o)phenone.


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Ketones: IUPAC nomenclature:

Parent = longest continuous carbon chain containing the carbonyl group. Alkane, drop –e, add –one. Prefix a locant for the position of the carbonyl using the principle of lower number.


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  • Aldehydes, syntheses:

  • Oxidation of 1o alcohols

  • Oxidation of methylaromatics

  • Reduction of acid chlorides

  • Ketones, syntheses:

  • Oxidation of 2o alcohols

  • Friedel-Crafts acylation

  • Coupling of R2CuLi with acid chloride


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Aldehydes synthesis 1) oxidation of primary alcohols:

RCH2-OH + K2Cr2O7, special conditions  RCH=O

RCH2-OH + C5H5NHCrO3Cl  RCH=O

(pyridinium chlorochromate)

[With other oxidizing agents, primary alcohols  RCOOH]


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Aldehyde synthesis: 2) oxidation of methylaromatics:

Aromatic aldehydes only!


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Aldehyde synthesis: 3) reduction of acid chloride


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Ketone synthesis: 1) oxidation of secondary alcohols


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Ketone synthesis: 2) Friedel-Crafts acylation

Aromatic ketones (phenones) only!


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Ketone synthesis: 3) coupling of RCOCl and R2CuLi


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  • Aldehydes & ketones, reactions:

  • Oxidation

  • Reduction

  • Addition of cyanide

  • Addition of derivatives of ammonia

  • Addition of alcohols

  • Cannizzaro reaction

  • Addition of Grignard reagents

  • 8) (Alpha-halogenation of ketones)

  • 9) (Addition of carbanions)


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nucleophilic addition to carbonyl:


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Mechanism:nucleophilic addition to carbonyl

1)

2)


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Mechanism:nucleophilic addition to carbonyl,acid catalyzed

1)

2)

3)


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  • 1) Oxidation

  • Aldehydes(very easily oxidized!)

  • CH3CH2CH2CH=O + KMnO4, etc.  CH3CH2CH2COOH

  • carboxylic acid

  • CH3CH2CH2CH=O + Ag+ CH3CH2CH2COO- + Ag

  • Tollen’s test for easily oxidized compounds like aldehydes.

  • (AgNO3, NH4OH(aq))

Silver mirror


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b) Methyl ketones:

Yellow ppt

test for methyl ketones


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  • 2) Reduction:

  • To alcohols


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Reduction

b) To hydrocarbons


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3) Addition of cyanide


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4) Addition of derivatives of ammonia


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5) Addition of alcohols


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  • Cannizzaro reaction. (self oxidation/reduction)

  • a reaction ofaldehydes without α-hydrogens


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Formaldehyde is the most easily oxidized aldehyde. When mixed with another aldehyde that doesn’t have any alpha-hydrogens and conc. NaOH, all of the formaldehyde is oxidized and all of the other aldehyde is reduced.

Crossed Cannizzaro:


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7) Addition of Grignard reagents.


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  • Planning a Grignard synthesis of an alcohol:

  • The alcohol carbon comes from the carbonyl compound.

  • The new carbon-carbon bond is to the alcohol carbon.

New carbon-carbon bond


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HX

Mg

ROH

RX

RMgX

larger

alcohol

H2O

ox.

R´OH

-C=O


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CH3 HBr CH3 Mg CH3

CH3CHCH2OH CH3CHCH2Br CH3CHCH2MgBr

H+

K2Cr2O7 CH3

CH3CH2OH CH3CH=O CH3CHCH2CHCH3

special cond. OH

4-methyl-2-pentanol


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Carboxylic Acids


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  • Carboxylic acids, syntheses:

  • oxidation of primary alcohols

  • RCH2OH + K2Cr2O7 RCOOH

  • 2.oxidation of arenes

  • ArR + KMnO4, heat  ArCOOH

  • 3.carbonation of Grignard reagents

  • RMgX + CO2 RCO2MgX + H+  RCOOH

  • 4.hydrolysis of nitriles

  • RCN + H2O, H+, heat  RCOOH


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  • oxidation of 1o alcohols:

  • CH3CH2CH2CH2-OH + CrO3 CH3CH2CH2CO2H

  • n-butyl alcohol butyric acid

  • 1-butanol butanoic acid

  • CH3 CH3

  • CH3CHCH2-OH + KMnO4  CH3CHCOOH

  • isobutyl alcohol isobutyric acid

  • 2-methyl-1-propanol` 2-methylpropanoic acid


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  • oxidation of arenes:

note: aromatic acids only!


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  • carbonation of Grignard reagent:

  • R-X RMgXRCO2MgX RCOOH

  • Increases the carbon chain by one carbon.

  • Mg CO2 H+

  • CH3CH2CH2-Br CH3CH2CH2MgBr CH3CH2CH2COOH

  • n-propyl bromide butyric acid

Mg CO2 H+


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  • Hydrolysis of a nitrile:

  • H2O, H+

  • R-CN R-CO2H

  • heat

  • H2O, OH-

  • R-CN R-CO2- + H+ R-CO2H

  • heat

  • R-X + NaCN  R-CN + H+, H2O, heat  RCOOH

  • 1o alkyl halide

  • Adds one more carbon to the chain.

  • R-X must be 1o or CH3!


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  • carboxylic acids, reactions:

  • as acids

  • conversion into functional derivatives

  • a)  acid chlorides

  • b)  esters

  • c)  amides

  • reduction

  • alpha-halogenation

  • EAS


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  • as acids:

  • with active metals

  • RCO2H + Na  RCO2-Na+ + H2(g)

  • with bases

  • RCO2H + NaOH  RCO2-Na+ + H2O

  • relative acid strength?

  • CH4 < NH3 < HCCH < ROH < HOH < H2CO3 < RCO2H < HF

  • quantitative

  • HA + H2O  H3O+ + A- ionization in water

  • Ka = [H3O+] [A-] / [HA]


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  • Conversion into functional derivatives:

  •  acid chlorides


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  •  esters

  • “direct” esterification:

  • RCOOH + R´OH  RCO2R´ + H2O

  • -reversible and often does not favor the ester

  • -use an excess of the alcohol or acid to shift equilibrium

  • -or remove the products to shift equilibrium to completion

  • “indirect” esterification:

  • RCOOH + PCl3 RCOCl + R´OH  RCO2R´

  • -convert the acid into the acid chloride first; not reversible


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  •  amides

  • “indirect” only!

  • RCOOH + SOCl2 RCOCl + NH3  RCONH2

  • amide

  • Directly reacting ammonia with a carboxylic acid results in an ammonium salt:

  • RCOOH + NH3 RCOO-NH4+

  • acid base


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  • Reduction:

  • RCO2H + LiAlH4; then H+ RCH2OH

  • 1o alcohol

  • Carboxylic acids resist catalytic reduction under normal conditions.

  • RCOOH + H2, Ni  NR


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  • Alpha-halogenation: (Hell-Volhard-Zelinsky reaction)

  • RCH2COOH + X2, P  RCHCOOH + HX

  • X

  • α-haloacid

  • X2 = Cl2, Br2


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5.EAS: (-COOH is deactivating and meta- directing)


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Functional Derivatives of Carboxylic Acids


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Nomenclature: the functional derivatives’ names are derived from the common or IUPAC names of the corresponding carboxylic acids.

Acid chlorides: change –ic acid to –yl chloride

Anhydrides: change acid to anhydride


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Amides: change –ic acid (common name) to –amide

-oic acid (IUPAC) to –amide

Esters: change –ic acid to –ate preceded by the name of the alcohol group


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Mechanism: Nucleophilic Acyl Substitution

1)

2)


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Mechanism:nucleophilic acyl substitution, acid catalyzed

1)

2)

3)


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Acid Chlorides

Syntheses:

SOCl2

RCOOH + PCl3 RCOCl

PCl5


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  • Acid chlorides, reactions:

  • Conversion into acids and derivatives:

  • a) hydrolysis

  • b) ammonolysis

  • c) alcoholysis

  • Friedel-Crafts acylation

  • Coupling with lithium dialkylcopper

  • Reduction


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acid chlorides: conversion into acids and other derivatives


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acid chlorides: Friedel-Crafts acylation


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acid chlorides: coupling with lithium dialkylcopper


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acid chlorides: reduction to aldehydes


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  • Anhydrides, syntheses:

  • Buy the ones you want!

  • Anhydrides, reactions:

  • Conversion into carboxylic acids and derivatives.

  • a) hydrolysis

  • b) ammonolysis

  • c) alcoholysis

  • 2) Friedel-Crafts acylation


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2) anhydrides, Friedel-Crafts acylation.


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Amides, synthesis:

Indirectly via acid chlorides.


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Amides, reactions.

1) Hydrolysis.


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  • Esters, syntheses:

  • From acids

  • RCO2H + R’OH, H+ RCO2R’ + H2O

  • From acid chlorides and anhydrides

  • RCOCl + R’OH RCO2R’ + HCl

  • From esters (transesterification)

  • RCO2R’ + R”OH, H+ RCO2R” + R’OH

  • RCO2R’ + R”ONa RCO2R” + R’ONa


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“Direct” esterification is reversible and requires use of LeChatelier’s principle to shift the equilibrium towards the products. “Indirect” is non-reversible.


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In transesterification, an ester is made from another ester by exchanging the alcohol function.


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  • Esters, reactions:

  • Conversion into acids and derivatives

  • a) hydrolysis

  • b) ammonolysis

  • c) alcoholysis

  • Reaction with Grignard reagents

  • Reduction

  • a) catalytic

  • b) chemical

  • 4) Claisen condensation


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Esters, reaction with Grignard reagents


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  • Esters, reduction

  • catalytic

  • chemical


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Carbanions

|

— C: –

|

The conjugate bases of weak acids,

strong bases, excellent

nucleophiles.


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1. Alpha-halogenation of ketones


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Carbanions. The conjugate bases of weak acids; strong bases, good nucleophiles.

1. enolate anions

2. organometallic compounds

3. ylides

4. cyanide

5. acetylides


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Aldehydes and ketones: nucleophilic addition

Esters and acid chlorides: nucleophilic acyl substitution

Alkyl halides: SN2

Carbanions as the nucleophiles in the above reactions.


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  • Carbanions as the nucleophiles in nucleophilic addition to aldehydes and ketones:

  • a) aldol condensation

  • “crossed” aldol condensation

  • b) aldol related reactions (see problem 21.18 on page 811)

  • c) addition of Grignard reagents

  • d) Wittig reaction


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a) Aldol condensation. The reaction of an aldehyde or ketone with dilute base or acid to form a beta-hydroxycarbonyl product.


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nucleophilic addition by enolate ion.


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Crossed aldol condensation:

If you react two aldehydes or ketones together in an aldol condensation, you will get four products. However, if one of the reactants doesn’t have any alpha hydrogens it can be condensed with another compound that does have alpha hydrogens to give only one organic product in a “crossed” aldol.

NaOH


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N.B. If the product of the aldol condensation under basic conditions is a “benzyl” alcohol, then it will spontaneouslydehydrate to the α,β-unsaturated carbonyl.


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  • Wittig reaction (synthesis of alkenes)

  • 1975 Nobel Prize in Chemistry to Georg Wittig

Ph = phenyl


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  • Carbanions as the nucleophiles in nucleophilic acyl substitution of esters and acid chlorides.

  • a) Claisen condensation

  • a reaction of esters that have alpha-hydrogens in basic solution to condense into beta-keto esters


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Mechanism for the Claisen condensation:


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Crossed Claisen condensation:


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Carbanions II

Carbanions as nucleophiles in SN2 reactions with alkyl halides.

a) Malonate synthesis of carboxylic acids

b) Acetoacetate synthesis of ketones

c) 2-oxazoline synthesis of esters/carboxylic acids

d) Organoborane synthesis of acids/ketones

e) Enamine synthesis of aldehydes/ketones


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Amines

(organic ammonia) :NH3

:NH2R or RNH21o amine(R may be Ar)

:NHR2 or R2NH2o amine

:NR3 or R3N3o amine

NR4+4o ammonium salt


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NB amines are classified by the class of the nitrogen, primary amines have one carbon bonded to N, secondary amines have two carbons attached directly to the N, etc.

Nomenclature.

Common aliphatic amines are named as “alkylamines”


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  • Amines, syntheses:

    • Reduction of nitro compounds1o Ar

  • Ar-NO2 + H2,Ni  Ar-NH2

    • Ammonolysis of 1o or methyl halidesR-X = 1o,CH3

      • R-X + NH3 R-NH2

    • Reductive aminationavoids E2

    • R2C=O + NH3, H2, Ni  R2CHNH2

    • Reduction of nitriles+ 1 carbon

    • R-CN + 2 H2, Ni  RCH2NH2

    • Hofmann degradation of amides- 1 carbon

    • RCONH2 + KOBr  RNH2


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1. Reduction of nitro compounds:


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  • Ammonolysis of 1o or methyl halides.


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3. Reductive amination:

Avoids E2


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  • Reduction of nitriles

  • R-CN + 2 H2, catalyst  R-CH2NH2

  • 1o amine

  • R-X + NaCN  R-CN  RCH2NH2

  • primary amine with one additional carbon

  • (R must be 1o or methyl)


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5. Hofmann degradation of amides


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  • Amine, reactions:

  • As bases

  • Alkylation

  • Reductive amination

  • Conversion into amides

  • EAS

  • Hofmann elimination from quarternary ammonium salts

  • Reactions with nitrous acid


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  • As bases

  • a) with acids

  • b) relative base strength

  • c) Kb

  • d) effect of groups on base strength


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2. Alkylation (ammonolysis of alkyl halides)


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3. Reductive amination


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  • Conversion into amides

  • R-NH2 + RCOCl  RCONHR + HCl

  • 1o N-subst. amide

  • R2NH + RCOCl  RCONR2 + HCl

  • 2o N,N-disubst. amide

  • R3N + RCOCl  NR

  • 3o


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  • EAS

  • -NH2, -NHR, -NR2 are powerful activating groups and ortho/para directors

  • a) nitration

  • b) sulfonation

  • c) halogenation

  • d) Friedel-Crafts alkylation

  • e) Friedel-Crafts acylation

  • f) coupling with diazonium salts

  • g) nitrosation


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a) nitration


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b) sulfonation


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c) halogenation


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  • Friedel-Crafts alkylation

  • NR with –NH2, -NHR, -NR2


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  • Friedel-Crafts acylation

  • NR with –NH2, -NHR, -NR2


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g) nitrosation


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h) coupling with diazonium salts  azo dyes


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  • Hofmann elimination from quarternary hydroxides

  • step 1, exhaustive methylation  4o salt

  • step 2, reaction with Ag2O  4o hydroxide + AgX

  • step 3, heat to eliminate  alkene(s) + R3N


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7. Reactions with nitrous acid


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Diazonium salts

synthesis

benzenediazonium ion


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  • Diazonium salts, reactions

  • Coupling to form azo dyes

  • Replacements

  • a) -Br, -Cl, -CN

  • b) -I

  • c) -F

  • d) -OH

  • e) -H

  • f) etc.


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coupling to form azo dyes


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Phenols Ar-OH

Phenols are compounds with an –OH group attached to an aromatic carbon. Although they share the same functional group with alcohols, where the –OH group is attached to an aliphatic carbon, the chemistry of phenols is very different from that of alcohols.


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Nomenclature.

Phenols are usually named as substituted phenols. The methylphenols are given the special name, cresols. Some other phenols are named as hydroxy compounds.


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  • phenols, syntheses:

  • From diazonium salts

  • 2. Alkali fusion of sulfonates


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  • phenols, reactions:

  • as acids

  • ester formation

  • ether formation

  • EAS

  • a) nitrationf) nitrosation

  • b) sulfonationg) coupling with diaz. salts

  • c) halogenationh) Kolbe

  • d) Friedel-Crafts alkylationi) Reimer-Tiemann

  • e) Friedel-Crafts acylation


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as acids:

with active metals:

with bases:

CH4 < NH3 < HCCH < ROH < H2O < phenols < H2CO3 < RCOOH < HF


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  • ester formation(similar to alcohols)


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  • ether formation (Williamson Synthesis)

  • Ar-O-Na+ + R-X  Ar-O-R + NaX

  • note: R-X must be 1o or CH3

  • Because phenols are more acidic than water, it is possible to generate the phenoxide in situ using NaOH.


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  • Electrophilic Aromatic Substitution

  • The –OH group is a powerful activating group in EAS and an ortho/para director.

  • a) nitration


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b) halogenation


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c) sulfonation

At low temperature the reaction is non-reversible and the lower Eact ortho-product is formed (rate control).

At high temperature the reaction is reversible and the more stable para-product is formed (kinetic control).


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d) Friedel-Crafts alkylation.


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e) Friedel-Crafts acylation


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Fries rearrangement of phenolic esters.


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f) nitrosation


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g) coupling with diazonium salts

(EAS with the weak electrophile diazonium)


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h) Kolbe reaction (carbonation)


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i) Reimer-Tiemann reaction


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Nomenclature

Syntheses

Reactions

Mechanisms

Spectroscopy


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Aromatic Hydrocarbons (Electrophilic Aromatic Substitution)

Spectroscopy (infrared & H-nmr)

Arenes

Aldehydes & Ketones

Carboxylic Acids

Functional Derivatives of Carboxylic Acids

Acid Chlorides, Anhydrides, Amides, Esters

Carbanions

Amines & Diazonium Salts

Phenols


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Mechanisms:

Electrophilic Aromatic Substitution

Nitration

Sulfonation

Halogenation

Friedel-Crafts Alkylation & Acylation

Nucleophilic Addition to Carbonyl

Nucleophilic Addition to Carbonyl, Acid Catalyzed

Nucleophilic Acyl Substitution

Nucleophilic Acyl Substitution, Acid Catalyzed


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