The document discusses organolithium compounds, highlighting their structure, reactivity, and preparation methods. These compounds are more reactive than Grignard reagents and can be synthesized from alkyl or aryl halides, through halogen-metal exchange, or metalation. Additionally, various chemical reactions involving organolithium compounds are detailed, including their interactions with active hydrogen compounds, carbonyls, and other organic substrates.

1. ORGANOLITHIUM
PREPARED BY: Zaeem
BS chemistry

2. Objectives
• To understand about structure of Organolithium compounds
• To understand about reactivity of Organolithium compounds

3. ORGANOLITHIUM COMPOUNDS
● The organolithium compounds are characterized by C-Li and
are important in Organic synthesis.
● Although ,Organolithium compounds show similar reactivity as
grignard reagents, they are more reactive than Grignard reagents.
● Lithium is less electronegative than carbon , and the C-Li bond is
polarized (C ¯-Li˖) as in Grignard regents.
● The Organolithium behaves both as Nucleophile and a base.

4. PREPARATION :
1) FROM ALKYL OR ARYL HALIDES:
The reaction of lithium metal at low temperature with an alkyl or aryl halide in a
Hydrocarbon solvent in inert atmosphere ( Nitrogen or Argon) gives an Alkyl
Lithium.
● The yield of alkyl-lithium is very low if pure lithium is used.
● It is believed that Lithium must contain at least 0.02% of sodium for the reaction
to proceed smoothly.
● In above reaction ,the reactivity of halides is : RI> RBr> RCl
ORGANOLITHIUM COMPOUNDS

5. 2) BY HALOGEN-METAL EXCHANGE METHOD:
This method is useful for the preparation of those Organolithium reagents
That can not be obtained from alkyl halide and metal directly. In this method , an
organic halides is treated with alkyl-Lithiums.
● This method is best suited for the preparation of Aryl-lithium derivatives.
● Thus , phenyl-lithium is prepared by treating bromo-benzene with n-butyl-lithium.
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ORGANOLITHIUM COMPOUNDS

6. 3) BY METALATION:
Compounds containing acidic hydrogen can be easily converted into
Organolithium compounds by treatment with a suitable Organolithium compound.
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ORGANOLITHIUM COMPOUNDS

7. PROPERTIES :
● Organolithium are very reactive ,powerful nucleophiles and strong bases.
● These find numerous application in organic synthesis.
● These are better than the Grignard reagents.
ORGANOLITHIUM COMPOUNDS

8. CHEMICAL REACTIONS
1) REACTIONS WITH COMPOUNDS CONTAINING ACTIVE
HYDROGEN:
The organolithium react with substrates having active hydrogen such as Water
alcohols ,amines (primary and secondary )and carboxylic acids to give the
corresponding hydrocarbons in quantitative yields.
In this respect ,the organolithium reagents resembles Grignard reagents.
ORGANOLITHIUM COMPOUNDS

9. 2) REACTION WITH CARBONYL COMPOUNDS :
● As in the case of Grignard reagents , the organolithiun reagents react with
aldehydes to form secondary alcohols and with ketones to form tertiary alcohols.
● Primary alcohols are obtained by treatment with formaldehyde.
● The yields of the alcohols ,in case of Organolithium is better that in case of
Grignard reagents.
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ORGANOLITHIUM COMPOUNDS

10. 11
2) REACTION WITH CARBONYL COMPOUNDS :
ORGANOLITHIUM COMPOUNDS

11. ● It has been stated that Grignard reagents (e.g.CH3MgBr) do
not react with hindered ketones.
● However , the Organolithium reagents are less susceptible to steric factors and react
with hindered ketones giving the corresponding tertiary alcohols.
● Organolithium reagents also react with esters to form the tertiary alcohols.
● The ketones that are initial products of reactions are more reactive than esters,
thus react further with organolithium reagents to yield alcohols.
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ORGANOLITHIUM COMPOUNDS
2) REACTION WITH CARBONYL COMPOUNDS :

12. 3) REACTION WITH ALKYL CYANIDE:
● Like Grignard reagents, the organolithium reagents also react with Alkyl cyanides to
give imine salts.
● When the reactions is worked up with water, protonation first gives the imine ,
which on acid hydrolysis generates the ketone.
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ORGANOLITHIUM COMPOUNDS

13. 4) REACTION WITH EPOXIDES:
● The epoxides react with organolithium reagents to give primary alcohols( as in case
of Grignard reagents).
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ORGANOLITHIUM COMPOUNDS

14. 5) REACTION WITH CARBON DIOXIDE:
● It is known that Grignard reagents on reaction with carbon dioxide give carboxylic
acids. However , in case of organolithium reagents, the formed carboxylate anion
reacts with a second molecule of the reagent to give a ketone.
● This method finds applications in the conversion of carboxylic acids into ketones.
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ORGANOLITHIUM COMPOUNDS

15. 6) REACTION WITH ALKENES:
• Organolithium reagents ( being more reactive than Grignard reagents) react with
alkenes to give alkyl-lithium, which reacts with a second molecule of the alkene to
give the corresponding alkyl-lithium.
• This process continues depending on the relative amount of the alkene.
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ORGANOLITHIUM COMPOUNDS

16. 7) ELECTROPHILIC DISPLACEMENT:
The reaction of an organic halide with an Organometallic compound
is known as Metal-halogen exchange reaction.
● This is an example of electrophilic displacement and finds use in
the synthesis of vinyl lithium from vinyl bromide.
● This method is useful for the preparation of phenyl lithium.
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ORGANOLITHIUM COMPOUNDS

17. 8) NUCLEOPHILIC DISPLACEMENT:
The halogen of the alkyl halides can be substituted with the alkyl group of the
organolithium reagent to give Hydrocarbons.
● This reaction takes place by SN2 mechanism as in the case of Wurtz reaction.
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ORGANOLITHIUM COMPOUNDS

18. ● The reaction of aryl halides with phenyl lithium take place via an elimination- addition pathway and not
via usual aromatic substitution reactions.
● In this reaction, phenyl lithium acts as strong base to abstract the O-hydrogen generating a carbanion
and also acts as nucleophile in addition to naphthyene.
8) NUCLEOPHILIC DISPLACEMENT:
ORGANOLITHIUM COMPOUNDS

19. 9)REACTION WITH α AND β –UNSATURATED CARBONYL
COMPOUNDS:
● It has been stated that Grignard reagents react with α and β-unsaturated carbonyl
compound giving 1,2- or 1,4-addition product depending on the structure of the c
carbonyl compound.
● The main reason is steric hinderance.
● The organolithium reagents on the other hand give exclusively 1,2-addition
Products.
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ORGANOLITHIUM COMPOUNDS

20. ● Exclusive formation of 1,4-addition product , can however ,
be achieved by use of Lithium dialkylcuprates
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ORGANOLITHIUM COMPOUNDS
9)REACTION WITH α AND β –UNSATURATED CARBONYL
COMPOUNDS: