dr. wolf's chm 201 & 202 14-1 chapter 14 organometallic compounds

Dr. Wolf's CHM 201 & 202 14-1

Chapter 14Chapter 14Organometallic CompoundsOrganometallic Compounds

Dr. Wolf's CHM 201 & 202 14-2

Organometallic Nomenclature

Dr. Wolf's CHM 201 & 202 14-3

Metal is the parentMetal is the parentMetal is the parentMetal is the parent LiLi

CyclopropylCyclopropyllithiumlithium VinylVinylsodiumsodium

HH22CC CHCHNaNa

CHCH33CHCH22MgMgCHCH22CHCH33

DiethylDiethylmagnesiummagnesium

CHCH33MgMgII

MethylMethylmagnesiummagnesiumiodideiodide

Dr. Wolf's CHM 201 & 202 14-4

Carbon-Metal BondsCarbon-Metal Bondsinin

Organometallic CompoundsOrganometallic Compounds

Dr. Wolf's CHM 201 & 202 14-5

FF 4.04.0 HH 2.12.1

OO 3.53.5 CuCu 1.91.9

NN 3.03.0 ZnZn 1.61.6

CC 2.52.5 AlAl 1.51.5

HH 2.1 2.1 MgMg 1.21.2

LiLi 1.01.0

NaNa 0.90.9

KK 0.80.8

ElectronegativitiesElectronegativities

Dr. Wolf's CHM 201 & 202 14-6

Polarity of BondsPolarity of BondsPolarity of BondsPolarity of Bonds

RR XX++ ––

RR MM–– ++

organometallics are a organometallics are a source of nucleophilic source of nucleophilic

carboncarbon

Dr. Wolf's CHM 201 & 202 14-7

Polarity of BondsPolarity of BondsPolarity of BondsPolarity of Bonds

CHCH33FF CHCH33LiLi

Dr. Wolf's CHM 201 & 202 14-8

Preparation of Organolithium CompoundsPreparation of Organolithium Compounds

Dr. Wolf's CHM 201 & 202 14-9

same for same for ArAr—X—X

An oxidation-reduction reaction: An oxidation-reduction reaction: carbon is reduced carbon is reduced

Organolithium CompoundsOrganolithium CompoundsOrganolithium CompoundsOrganolithium Compounds

RR X + 2LiX + 2Li RR Li + LiXLi + LiX

normally prepared by reaction of alkyl halides normally prepared by reaction of alkyl halides with lithiumwith lithium

Dr. Wolf's CHM 201 & 202 14-10

ExamplesExamplesExamplesExamples

(CH(CH33))33CCl + 2LiCCl + 2Li

diethyldiethyletherether

––10°C10°C

(CH(CH33))33CLi + LiClCLi + LiCl

(75%)(75%) BrBr + 2Li+ 2Li


35°C35°C

LiLi + LiBr+ LiBr

(95-99%)(95-99%)

Dr. Wolf's CHM 201 & 202 14-11

Electron BookkeepingElectron BookkeepingElectron BookkeepingElectron Bookkeeping

RR X + LiX + Li [R[R X]X] + Li+ Li++••––

RR•• ++ •••• XX––

••

LiLi••••••RR LiLi

Dr. Wolf's CHM 201 & 202 14-12

Preparation of Organomagnesium Compounds:

Grignard Reagents

Dr. Wolf's CHM 201 & 202 14-13

same for same for ArAr—X—X

Grignard ReagentsGrignard ReagentsGrignard ReagentsGrignard Reagents

RR X + MgX + Mg RMgXRMgX

prepared by reaction of alkyl halides prepared by reaction of alkyl halides with magnesiumwith magnesium

Diethyl ether is most often used solvent. Diethyl ether is most often used solvent. Tetrahydrofuran is also used.Tetrahydrofuran is also used.

Dr. Wolf's CHM 201 & 202 14-14

ExamplesExamplesExamplesExamplesdiethyldiethyletherether

––10°C10°C(96%)(96%)

BrBr + Mg+ Mg


35°C35°C

MgBrMgBr

(95%)(95%)

ClCl + Mg+ Mg

MgClMgCl

Dr. Wolf's CHM 201 & 202 14-15

RR X + MgX + Mg

Electron BookkeepingElectron BookkeepingElectron BookkeepingElectron Bookkeeping

[R[R X]X] + Mg+ Mg++••––

RR•• ++ •••• XX––

••

••••RR MgMg++

•• ••

MgMg++••

•••• XX––

Dr. Wolf's CHM 201 & 202 14-16

I > Br > Cl >> FI > Br > Cl >> F

RX > ArXRX > ArX

Order of ReactivityOrder of ReactivityOrder of ReactivityOrder of Reactivity

Dr. Wolf's CHM 201 & 202 14-17

certain groups cannot be present incertain groups cannot be present in

the solventthe solvent

the halide from which the Grignard reagent the halide from which the Grignard reagent

is preparedis prepared

the substance with which the Grignard the substance with which the Grignard reagent reactsreagent reacts

Forbidden GroupsForbidden GroupsForbidden GroupsForbidden Groups

Dr. Wolf's CHM 201 & 202 14-18

Anything with an OH, SH, or NH groupAnything with an OH, SH, or NH groupi.e. an acidic hydrogeni.e. an acidic hydrogen

Forbidden GroupsForbidden GroupsForbidden GroupsForbidden Groups

therefore cannot use Htherefore cannot use H22O, CHO, CH33OH, OH,

CHCH33CHCH22OH, etc. as solventsOH, etc. as solvents

cannot prepare Grignard reagent from cannot prepare Grignard reagent from substances such as HOCHsubstances such as HOCH22CHCH22Br, etc.Br, etc.

Dr. Wolf's CHM 201 & 202 14-19

Organolithium and Organomagnesium Compounds as Brønsted Bases

Dr. Wolf's CHM 201 & 202 14-20

Brønsted basicityBrønsted basicityBrønsted basicityBrønsted basicity

RR

MM

HH

OR'OR'

••••

••••

RR HH

OR'OR'••••

••••••••––

MM++

–– ++

Grignard reagents (Grignard reagents (MM = MgX) and = MgX) and organolithium reagents (organolithium reagents (MM = Li) are strong = Li) are strong bases.bases.

Dr. Wolf's CHM 201 & 202 14-21

ExampleExampleExampleExample

(100%)(100%)

+ H+ H22OO

++ LiOHLiOH

CHCH33CHCH22CHCH22CHCH22LiLi

CHCH33CHCH22CHCH22CHCH33

water is a stronger water is a stronger acid than butaneacid than butane

Dr. Wolf's CHM 201 & 202 14-22

ExampleExampleExampleExample MgBrMgBr

(100%)(100%)

+ CH+ CH33OHOH ++ CHCH33OMgBrOMgBr

methanol is a methanol is a stronger acid than stronger acid than benzenebenzene

Dr. Wolf's CHM 201 & 202 14-23

Table 14.2Table 14.2Approximate Acidities of HydrocarbonsApproximate Acidities of Hydrocarbons

Table 14.2Table 14.2Approximate Acidities of HydrocarbonsApproximate Acidities of Hydrocarbons

HydrocarbonHydrocarbon ppKKaa

(CH(CH33))33CCHH 7171

CHCH33CHCH33 6262

CHCH44 6060

EthyleneEthylene 4545

BenzeneBenzene 4343

AmmoniaAmmonia 3636

AcetyleneAcetylene 2626

WaterWater 1616

Hydrocarbons are Hydrocarbons are very weak acids.very weak acids.

Their conjugate Their conjugate bases are very bases are very strong bases.strong bases.

Grignard reagents Grignard reagents and organolithium and organolithium reagents are strong reagents are strong bases.bases.

Dr. Wolf's CHM 201 & 202 14-24

Acetylenic Grignard ReagentsAcetylenic Grignard ReagentsAcetylenic Grignard ReagentsAcetylenic Grignard Reagents

are prepared by an acid-base reactionare prepared by an acid-base reaction

CHCH33CHCH22MgMgBrBr

++CHCH33CHCH33

stronger acidstronger acid

weaker acidweaker acid

HCHC CHCH

HCHC CCMgMgBrBr

++

Dr. Wolf's CHM 201 & 202 14-25

Synthesis of Alcohols Using Synthesis of Alcohols Using

Grignard ReagentsGrignard Reagents

Dr. Wolf's CHM 201 & 202 14-26

Grignard reagents act as nucleophilesGrignard reagents act as nucleophilestoward the carbonyl grouptoward the carbonyl group

Grignard reagents act as nucleophilesGrignard reagents act as nucleophilestoward the carbonyl grouptoward the carbonyl group

RR

MgXMgX

CC

OO

••••

•••• ––MgXMgX++

–– ++RR CC

OO••••

•••• ••••

••••

RR CC

OHOH••••

HH33OO++


two-step sequence two-step sequence gives an alcohol as gives an alcohol as the isolated product the isolated product

Dr. Wolf's CHM 201 & 202 14-27

formaldehydeformaldehyde to give primary alcohols to give primary alcohols

aldehydesaldehydes to give secondary alcohols to give secondary alcohols

ketonesketones to give tertiary alcohols to give tertiary alcohols

estersesters to give tertiary alcohols to give tertiary alcohols

Grignard reagents react with:Grignard reagents react with:Grignard reagents react with:Grignard reagents react with:

Dr. Wolf's CHM 201 & 202 14-28



Dr. Wolf's CHM 201 & 202 14-29

Grignard reagents react with Grignard reagents react with formaldehydeformaldehydeGrignard reagents react with Grignard reagents react with formaldehydeformaldehyde

RR

MgXMgX

CC

OO

••••


–– ++RR CC

OO••••

•••• ••••

••••

RR CC

OHOH••••

HH33OO++


product is a product is a primary alcoholprimary alcohol

HH HHHH

HH

HH

HH

Dr. Wolf's CHM 201 & 202 14-30



ClCl

MgMg

MgClMgCl

CC OO

HH

HH CCHH22OMgClOMgCl

HH33OO++

CCHH22OHOH

(64-69%)(64-69%)

Dr. Wolf's CHM 201 & 202 14-31




Dr. Wolf's CHM 201 & 202 14-32

Grignard reagents react with Grignard reagents react with aldehydesaldehydesGrignard reagents react with Grignard reagents react with aldehydesaldehydes

RR

MgXMgX

CC

OO

••••

•••• ––

–– ++RR CC

OO••••

•••• ••••

••••

RR CC

OHOH••••

HH33OO++


product is a product is a secondary alcoholsecondary alcohol

HH R'R'HH

R'R'

HH

R'R'

MgXMgX++

Dr. Wolf's CHM 201 & 202 14-33



MgMg

CC OO

HH33CC

HH

HH33OO++

(84%)(84%)

CHCH33(CH(CH22))44CHCH22BrBr CHCH33(CH(CH22))44CHCH22MgBrMgBr

CHCH33(CH(CH22))44CHCH22CCHHCHCH33

OMgBrOMgBr

CHCH33(CH(CH22))44CHCH22CCHHCHCH33

OHOH

Dr. Wolf's CHM 201 & 202 14-34



ketonesketones to give tertiary alcohols to give tertiary alcohols


Dr. Wolf's CHM 201 & 202 14-35

Grignard reagents react with Grignard reagents react with ketonesketonesGrignard reagents react with Grignard reagents react with ketonesketones

RR

MgXMgX

CC

OO

••••


–– ++RR CC

OO••••

•••• ••••

••••

RR CC

OHOH••••

HH33OO++


product is a product is a tertiary alcoholtertiary alcohol

R"R" R'R'R"R"

R'R'

R"R"

R'R'

Dr. Wolf's CHM 201 & 202 14-36



MgMg

HH33OO++

(62%)(62%)

CHCH33ClCl CHCH33MgClMgCl OO CHCH33ClMgOClMgO CHCH33HOHO

Dr. Wolf's CHM 201 & 202 14-37

Organolithium reagents react with Organolithium reagents react with aldehydes and ketones in the same aldehydes and ketones in the same

way that Grignard reagents do.way that Grignard reagents do.

Synthesis of AlcoholsUsing Organolithium Reagents

Dr. Wolf's CHM 201 & 202 14-38


(76%)(76%)

HH22CC CHLiCHLi ++

CCHH

OO

1. diethyl ether1. diethyl ether

2. H2. H33OO++ CHCH22CCHCHHCH

OHOH

Dr. Wolf's CHM 201 & 202 14-39

Synthesis of Acetylenic Alcohols

Dr. Wolf's CHM 201 & 202 14-40

Using Sodium Salts of AcetylenesUsing Sodium Salts of AcetylenesUsing Sodium Salts of AcetylenesUsing Sodium Salts of Acetylenes

HCHC CHCH

NaNHNaNH22

NHNH33

HCHC CCNaNa

HCHC CCNaNa ++1. NH1. NH33

2. H2. H33OO++

OO HOHO CC CCHH (65-75%)(65-75%)

Dr. Wolf's CHM 201 & 202 14-41

CHCHCHCH33(CH(CH22))33CC ++ CHCH33CHCH22MgMgBrBr

CCMgMgBrBrCHCH33(CH(CH22))33CC ++ CHCH33CHCH33

diethyl etherdiethyl ether

1. H1. H22CC OO2. H2. H33OO++

CCCCHH22OHOHCHCH33(CH(CH22))33CC

(82%)(82%)

Using Acetylenic Grignard ReagentsUsing Acetylenic Grignard ReagentsUsing Acetylenic Grignard ReagentsUsing Acetylenic Grignard Reagents

Dr. Wolf's CHM 201 & 202 14-42

Retrosynthetic Analysis

Retrosynthetic analysis is the process by Retrosynthetic analysis is the process by which we plan a synthesis by reasoning which we plan a synthesis by reasoning backward from the desired product (the backward from the desired product (the "target molecule")."target molecule").

Dr. Wolf's CHM 201 & 202 14-43

Retrosynthetic Analysis of AlcoholsRetrosynthetic Analysis of AlcoholsRetrosynthetic Analysis of AlcoholsRetrosynthetic Analysis of Alcohols

CC

OHOH

Step 1 Step 1 Locate the carbon that bears the Locate the carbon that bears the hydroxyl group.hydroxyl group.

Dr. Wolf's CHM 201 & 202 14-44


CC

OHOH

Step 2 Step 2 Disconnect one of the groups Disconnect one of the groups attached to this carbon.attached to this carbon.

Dr. Wolf's CHM 201 & 202 14-45


CC

OHOH

Dr. Wolf's CHM 201 & 202 14-46


CC

OO

What remains is the combination of Grignard What remains is the combination of Grignard reagent and carbonyl compound that can be reagent and carbonyl compound that can be used to prepare the alcohol.used to prepare the alcohol.

MgXMgX

Dr. Wolf's CHM 201 & 202 14-47

ExampleExampleExampleExample CC

OHOH

CHCH33

CHCH22CHCH33

CC CHCH22CHCH33

OO

CHCH33MgXMgX

There are two There are two other other possibilities. possibilities.

Can you see Can you see them?them?

Dr. Wolf's CHM 201 & 202 14-48

SynthesisSynthesisSynthesisSynthesis

CC

OHOH

CHCH33

CHCH22CHCH33

CC CHCH22CHCH33

OO

1.1.

2. H2. H33OO++

CHCH33BrBrMgMg, diethyl ether, diethyl ether

CHCH33MgMgBrBr

Dr. Wolf's CHM 201 & 202 14-49

Preparation of Tertiary AlcoholsFrom Esters and Grignard Reagents

(also in Chapter 19)

Dr. Wolf's CHM 201 & 202 14-50

Grignard reagents react with estersGrignard reagents react with estersGrignard reagents react with estersGrignard reagents react with esters

RR

MgXMgX

CC

OO

••••


–– ++RR CC

OO••••

•••• ••••


OCHOCH33••••

•••• OCHOCH33••••

••••

R'R'R'R'

but species formed is but species formed is unstable and dissociates unstable and dissociates under the reaction under the reaction conditions to form a ketoneconditions to form a ketone

Dr. Wolf's CHM 201 & 202 14-51

Grignard reagents react with estersGrignard reagents react with estersGrignard reagents react with estersGrignard reagents react with esters

RR

MgXMgX

CC

OO

••••


–– ++RR CC

OO••••

•••• ••••


OCHOCH33••••

•••• OCHOCH33••••

••••

R'R'R'R'

––CHCH33OOMgXMgX

CC

OO

RR R'R'

••••••••

this ketone then goes this ketone then goes on to react with a on to react with a second mole of the second mole of the Grignard reagent to Grignard reagent to give a tertiary alcoholgive a tertiary alcohol

Dr. Wolf's CHM 201 & 202 14-52


2 CH2 CH33MgBrMgBr ++ (CH(CH33))22CHCCHCOCHOCH33

OO

1. diethyl ether1. diethyl ether

2. H2. H33OO++

(CH(CH33))22CHCCHCCHCH33

OHOH

CHCH33

(73%)(73%)

Two of the groups Two of the groups attached to the attached to the tertiary carbon tertiary carbon come from the come from the Grignard reagentGrignard reagent

Dr. Wolf's CHM 201 & 202 14-53

Alkane Synthesis Using Alkane Synthesis Using Organocopper ReagentsOrganocopper Reagents

Dr. Wolf's CHM 201 & 202 14-54

Lithium dialkylcuprates are useful synthetic Lithium dialkylcuprates are useful synthetic reagents.reagents.

They are prepared from alkyllithiums and a They are prepared from alkyllithiums and a copper(I) halide.copper(I) halide.

2RLi + 2RLi + CuCuXX RR22CuCuLi + LiLi + LiXX

[customary solvents are diethyl ether and [customary solvents are diethyl ether and tetrahydrofuran (THF)]tetrahydrofuran (THF)]

Lithium DialkylcupratesLithium DialkylcupratesLithium DialkylcupratesLithium Dialkylcuprates

Dr. Wolf's CHM 201 & 202 14-55

the alkyllithium first reacts with the copper(I) the alkyllithium first reacts with the copper(I) halidehalide

How?How?How?How? RR LiLi

CuCu II

LiLi++RR

CuCu II––

Dr. Wolf's CHM 201 & 202 14-56

the alkyllithium first reacts with the copper(I) the alkyllithium first reacts with the copper(I) halidehalide

then a second molecule of the alkyllithium then a second molecule of the alkyllithium reacts with the alkylcopper species formed in reacts with the alkylcopper species formed in the first stepthe first step

LiLi++

––

How?How?How?How? RR LiLi

CuCu II

LiLi++RR

CuCu II––

RR LiLi

RR CuCu

RR

CuCuRR

Dr. Wolf's CHM 201 & 202 14-57

RR22CuCuLiLi ++ R'R'XX RR R'R' ++ RRCuCu ++ LiLiXX

ArAr22CuCuLiLi ++ R'R'XX ArAr R'R' ++ ArArCuCu ++ LiLiXX

Lithium diorganocuprates are used toLithium diorganocuprates are used toform C—C bondsform C—C bonds

Lithium diorganocuprates are used toLithium diorganocuprates are used toform C—C bondsform C—C bonds

Dr. Wolf's CHM 201 & 202 14-58

primary alkyl halides work best (secondary and primary alkyl halides work best (secondary and tertiary alkyl halides undergo elimination)tertiary alkyl halides undergo elimination)


(CH(CH33))22CuCuLiLi ++ CHCH33(CH(CH22))88CHCH22II

CHCH33(CH(CH22))88CHCH22CHCH33

(90%)(90%)

Example: Lithium Example: Lithium dimethyldimethylcupratecuprateExample: Lithium Example: Lithium dimethyldimethylcupratecuprate

Dr. Wolf's CHM 201 & 202 14-59

Example: Lithium Example: Lithium diphenyldiphenylcupratecuprateExample: Lithium Example: Lithium diphenyldiphenylcupratecuprate


(C(C66HH55))22CuCuLiLi ++ CHCH33(CH(CH22))66CHCH22II

CHCH33(CH(CH22))66CHCH22CC66HH55

(99%)(99%)

Dr. Wolf's CHM 201 & 202 14-60

(CH(CH33CHCH22CHCH22CHCH22))22CuLiCuLi

Vinylic halides can be usedVinylic halides can be usedVinylic halides can be usedVinylic halides can be used

++


BrBr


(80%)(80%)

Dr. Wolf's CHM 201 & 202 14-61

(CH(CH33CHCH22CHCH22CHCH22))22CuLiCuLi

Aryl halides can be usedAryl halides can be usedAryl halides can be usedAryl halides can be used

++


II


(75%)(75%)

Dr. Wolf's CHM 201 & 202 14-62

An Organozinc Reagent An Organozinc Reagent forfor

Cyclopropane SynthesisCyclopropane Synthesis

Dr. Wolf's CHM 201 & 202 14-63

Iodomethylzinc iodideIodomethylzinc iodideIodomethylzinc iodideIodomethylzinc iodide

reacts with alkenes to form cyclopropanesreacts with alkenes to form cyclopropanes

reaction with alkenes is called thereaction with alkenes is called theSimmons-Smith reactionSimmons-Smith reaction

CHCH22II22 + Zn + Zn ICHICH22ZnIZnICuCu

formed by reaction of diiodomethane withformed by reaction of diiodomethane withzinc that has been coated with copperzinc that has been coated with copper(called zinc-copper couple)(called zinc-copper couple)

Dr. Wolf's CHM 201 & 202 14-64



HH22CC CC

CHCH22CHCH33

CHCH33

CHCH22II22, Zn/Cu, Zn/Cu CHCH22CHCH33

CHCH33

(79%)(79%)I CHI CH22 ZnI ZnI

via

Dr. Wolf's CHM 201 & 202 14-65

Stereospecific syn-additionStereospecific syn-additionStereospecific syn-additionStereospecific syn-addition

diethyl etherdiethyl etherCHCH22II22, Zn/Cu, Zn/Cu

CC CC

CHCH33CHCH22 CHCH22CHCH33

HH HH CHCH33CHCH22 CHCH22CHCH33

HH HH

Dr. Wolf's CHM 201 & 202 14-66

Stereospecific syn-additionStereospecific syn-additionStereospecific syn-additionStereospecific syn-addition

diethyl etherdiethyl etherCHCH22II22, Zn/Cu, Zn/Cu

CC CC

CHCH33CHCH22

CHCH22CHCH33HH

HH

CHCH33CHCH22

CHCH22CHCH33HH

HH

Dr. Wolf's CHM 201 & 202 14-67

Carbenes and CarbenoidsCarbenes and Carbenoids

Dr. Wolf's CHM 201 & 202 14-68

CarbeneCarbeneCarbeneCarbene

name to give to species that contains aname to give to species that contains adivalent carbon (carbon with two bondsdivalent carbon (carbon with two bondsand six electrons)and six electrons)

CC••••

BrBr BrBr

DibromocarbeneDibromocarbene

(same chemistry with dichlorocarbenes)(same chemistry with dichlorocarbenes)Carbenes are very reactive; normally cannot be isolated and Carbenes are very reactive; normally cannot be isolated and

stored.stored.Are intermediates in certain reactions.Are intermediates in certain reactions.

Dr. Wolf's CHM 201 & 202 14-69

Generation of DibromocarbeneGeneration of DibromocarbeneGeneration of DibromocarbeneGeneration of Dibromocarbene

CC

BrBr

BrBr

BrBr

HH ++ OC(CHOC(CH33))33

––

••••

••••••••

HH++ OC(CHOC(CH33))33••••

••••CC

BrBr

BrBr

BrBr

––••••

Dr. Wolf's CHM 201 & 202 14-70

Generation of DibromocarbeneGeneration of DibromocarbeneGeneration of DibromocarbeneGeneration of Dibromocarbene

++

CC

BrBr

BrBr

BrBr

––••••

CC••••

BrBr BrBr BrBr––

Dr. Wolf's CHM 201 & 202 14-71

Carbenes react with alkenesCarbenes react with alkenesto give cyclopropanesto give cyclopropanes

Carbenes react with alkenesCarbenes react with alkenesto give cyclopropanesto give cyclopropanes

+ CHBr+ CHBr33

BrBr

BrBr

(75%)(75%)

CBrCBr22 is an intermediate is an intermediate

stereospecific syn additionstereospecific syn addition

KOC(CHKOC(CH33))33

(CH(CH33))33COHCOH

End of Chapter 14

dr. wolf's chm 201 & 202 14-1 chapter 14 organometallic compounds

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