Halogenoalkanes Flashcards
What are the three structural types of monohalogenoalkanes classified according to?
The number of alkyl groups attached to the carbon atom bearing the halogen atom.
What is the main type of reaction a monohalogenoalkane will undergo?
Nucleophilic substitution
What is the importance of the polar carbon to halogen bond?
It makes the halogen susceptible to nucleophilic attack.
What does the incoming nucleophile do to the slight positive carbon?
The nucleophile donates an electron pair and in doing so , forms a covalent bond with the carbon atom. The halogen is thrown out and substituted by the nucleophile.
What is the reaction between a monohalogenoalkane and:
- Ammonia
- Ethanolic cyanides
- Alkalis
- Alcoholic Alkoxides
Ammonia- Ammine (R-NH2)
Ethanolic KCN - Nitrile (R-CN)(Useful as it increases chain length)
KOH- Alcohol
Alkoxide- An ether
What is an alkoxide?
When an alkali metal is added to an alcohol. Hydrogen gas is released and potassium takes the place of hydrogen but is an ion
What reaction might follow the production of a nitrile?
Acid hydrolysis, to form a carboxylic acid
What are the two types of nucleophilic substitution mechanism a monohalogenoalkane can undertake?
Sn1 ans Sn2
How many steps is an Sn1 reaction?
2 step process
What does the rate depend on in an Sn1 reaction?
The concentration of the halogenoalkane (1 molecule)
Describe step 1 in an Sn1 reaction
A slow rate determining step as it involves only the halogenoalkane.
What happens during step 1 and 2 of the nucleophilic substitution of an Sn1 reaction.
The Nucleophile leaves the molecule forming a carbocation intermediate.
A new nucleophile then comes and donates electrons to the carbocation intermediate forming a covalent bond.
What type of monohalogenoalkane does an Sn1 reaction usually involve?
Tertiary
How many steps does an Sn2 reaction have?
1
What does the rate determining step of an Sn2 reaction involve?
Both the hologenoalkane and the nucleophile
