Carbon-carbon Bond Formation Flashcards
How can the carbon chain be extended in organic molecules?
C-C bond formation
Why is C-C bond formation useful in synthesis?
In order to form new molecules
What is used to add an extra carbon to a carbon chain?
Nitriles and then other reactions can be carried out to change the nitrile group into another functional group.
how can carbon chain length be increased through Nucleophilic substition reaction?
haloalkanes contain polar carbon-halogen bond. Halogen more electronegative than carbon so makes carbon electron deficient.
Reflux a haloalkane with potassium cyanide or sodium cyanide (KCN or NaCN) in ethanol the haloalkane and cyanide ions will react to form a nitrile.
Draw a reaction mechanism between bromoethane and KCN. (Nucleophilic substitution)
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How can carbon chain length be increased through Nucleophilic addition reaction?
Nucleophile are able attack a molecule with a carbonyl group. (Aldehydes and ketones contain a polar C=O bond).
If you react them with HCN (hydrogen cyanide), the cyanide ion will react with the carbon centre to form a hydroxynitrile. (Hydroxynitrile is produced because the oxygen atom is protonated).
Draw a mechanism for a Nucleophilic addition reaction between a ketone and HCN.
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How can amines be produced from nitriles? What are the conditions and reagents
Reduction (called hydrogenation)
Requires hydrogen with a nickel catalyst. (Catalytic hydrogenation)
How can carboxylic acids be produced from nitriles?
Acid hydrolysis. The nitrile is heated under reflux with dilute aqueous acid to form the carboxylic acid and ammonium salt. You can do the same for a hydroxynitrile as well. It will form a hydroxycarboxlic acid,
How can a C-C bond be introduced into an aromatic compound?
Using Friedel-Crafts Alkylation or Friedel-Crafts Acylation. Both reactions occur in the presence of a halogen carrier to make the strong electrophile and allow electrophilic substitution to occur.
How does friedel-crafts acylation work?
Write relevant equations and a mechanism
It substitutes an acyl group for a hydrogen atom on the benzene ring. The electrophilic reactive intermediate is produced from a reaction between the acyl chloride and an aluminium chloride catalyst.
R-COCl + AlCl3 = R-CO+ + AlCl4-
The electrophile is then attacked by the benzene ring, which is the mechanism.
Check on pmt
At the end of the reaction, the H+ ion removed from the ring reacts with the AlCl4- ion to reform the aluminium chloride, indicating it to be a catlayst. steamy fumes of HCl gas is also released.
H+ + AlCl4- = AlCl3 + HCl
How does friedel crafts alkylation work?
Substitutes an alkyl group for a hydrogen atom on the benzene ring. The electrophilic reactive intermediate is produced from a reaction between a haloalkane and aluminium chloride catalyst.
R-CH2Cl + AlCl3 = R-CH2+ + AlCl4-
The electrophile is then attacked by the benzene ring which is shown in a mechanism.
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