Organometallic Compounds

Question 1

Formation of an Organolithium Compound

Answer 1

Reactant: Alkyl Halide

Reagents: 2 Li and hexane

Product: A carbon chain with lithium attached

For example:

1-bromobutane turns into butyllithium

More reactive

Can form from alkyl halides (usually alkyl bromide), aryl halides, and vinyliv halides.

Cannot form from OH, NH₂, NHR, SH, C(triple bond)CH, COOH)

Question 2

Formation of an Organomagensium Compound (Grignard Reagents)

Answer 2

Reactant: Alkyl Halide

Reagents: Mg and THF or diethyl ether

Product: Carbon chain with a magnesium attached and then a bromine

For Example: vinyl bromide turns into vinylmagnesium bromide

Less Reactive

Can form from alkyl halides (usually alkyl bromide), aryl halides, and vinyliv halides. Cannot form from OH, NH2, NHR, SH, C(triple bond)CH, COOH)

Question 3

Transmetallation

Answer 3

Reactant: organometallic compound

Reagent: a metal halide that contains a metal that is more electronegative than the one in the reactant

Product: organometallic compound where the 2 metals switch place

For example: ethyl magnesium chloride in cadmium chloride would turn into diethylcadmium

Question 4

Formation of an organocuprates (Gliman Reagent)

Answer 4

Reactant: 2 organolithium compounds and CuI

Reagent: THF

Product: an organocuprate

For example: 2 CH₃Li + CuI= (CH₃)₂CuLi +LiI

Question 5

Reaction of an Organocuprate

Answer 5

Reactants: Organocuprate and an alkyl halide

Product: 1 of the carbon chains of the organocuprate replaces the halogen

Only works with HI, HBr, and HCl..does not work with HF

Can react with the R group on any alkyl halide except secondary or tertiary.

Reaction is stereospecific, so the stereochemistry of the double bond (cis or trans) is maintained.

Can replace halogens in compounds with other functional groups.

Can open an epoxide, the carbon chain will attack the least substituted side of the epoxide and open it up.

Question 6

Organolithium and Organomagnesium Reactions

Answer 6

SN2 attack, where the bond attached to the Li or Mg acts as a carbanion and performs a SN2 attack. Cannot attack vinylic and aryl halides.

Question 7

Suzuki Reaction

Answer 7

Reactant: A vinyl or an aryl halide and an organoboron compound

Reagent: L₂Pd and ^-OH

Product: varies

Remove a hydrogen from the transposition and remaining stereospecificity replace it with the carbon chain or the organoboron compound. If attaching an alkene, always attach it as a trans alkene.

Question 8

Preparing the organoboron compound

Answer 8

Reactant: an alkene or an alkyne and catachelborane HBr(OR)₂

Product: the catechelborane with the hydrogen being switched out for the carbon chain after it has lost a bond (double bond–> single bond, triple bond–>double bond).

This is done through hydroborationof a terminal alkene or alkyne.

Question 9

Formation of an aryl-organoboron compound

Answer 9

Reactant: an organolithium compound benzyllithium and trimethylborate B(OCH₃)₃

Product: an aryl organoboron

Question 10

Heck Reaction

Answer 10

Reactant: a vinylic or aryl halide and an alkene

Reagents: L₂Pd and TEA

Product: the carbon chain on the vinylic or aryl halide replaces a trans hydrogen on the alkene

Prefer a symmetrical alkene, terminal alkene (because less steric hinderence), and an sp2 carbon bonded to an electron withdrawing group

Question 11

Metathesis

Question 12

What type of reagents can we make?

Answer 12

• Gringard and Lithium: Primary, Secondary, and Tertiary Halide, Alkenyl Halide, and an Aryl Halide
• Gillman: Primary Halide, Alkenyl Halide, and Aryl Halide
• Suzuki: Primary, Alkeny, or Aryl organoboron
• Heck: Alkenyl Halide

Question 13

What can we couple to?

Answer 13

• Grignard and Lithium: Primary Alkyl
• Gilman: Primary alkyl halide, alkenyl, and aryl halde
• Suzuki: Alkenyl or Aryl Halide
• Heck: Alkenyl or Aryl Halide