15.1 Flashcards
What are haloalkanes?
Compounds containing the elements acrbon, hydrogen and at least one halogen.
What is added in order to identify a halogen?
A prefix- iodo refers to iodine
Fluro refers to fluorine
Chloro refers to chlorine
Bromo refers to bromine
Is the carbon-halogen bond polar or not?
Yes it is polar- because the halogen is more electronegative than the carbon atoms. The carbon atom will be slightly delta positive and will be able to attract a lone pair of electrons.
What is a nucleophile?
A species that can donate a lone pair of electrons
What are some examples of nucleophiles?
:OH- , :H20, :NH3-, :Br- (things that are negatively charged make good nucleophiles)
How can haloalkanes be classified?
As primary, secondary and tertiary.
How do primary haloalkanes look like?
One carbon atom directly adjoining the carbon atom that contains the halogen
What do secondary haloalkanes look like?
Two carbon atoms directly adjoining the carbon atom that contains the halogen
What do tertiary haloalkanes look like?
3 carbon atojms directly attached to the carbon atom containing the halogen
What is nucleophlilic subsitution?
Primary haloalkane reacts with nucleophile, the nucleophile replaces the halogen in a subsitution reaction (nucleophilic subsitution)
What is the reaction between CH3CL + OH- —->CH3OH + Cl-
OH- is the nucleophile Attracted to the carbon atom as it is slightly delta positive The bond is broken by hetrolytic fission and the reaction is generally done under reflux The halogen (Cl) ends up getting displaced.
What does the rate of subsitution reactions depend on?
The strength of the C-X bond. Weaker bond, easier to break and faster reaction.
What are hydrolysis reactions?
Chemical reactions involving water or aqueous solution of a hydroxide that breaks a bond.
It is dependent on average bond enthaply (measurement of covalent bond strength)
How can haloalkanes be converted into alcohols?
Using aqueous alkali, like sodium/potassiumhydroxide to produce an alkali in nucleophillic subsitution reaction. It is heated under reflux to obtain a good yield of product.
Does the relative reactivity of halogens increase/decrease down the group?
Electronegativity of halogens decrease down the group. The carbo-fluroine bond is more polar than the carbo-iodine bond. The increased polarity, along w the fact that the carbo-fluroine bond is shorter than the carbo-fluroine bond is stronger than the carbo-iodine bond. Therefore the reactivity is dependent on the halogen present in the molecule.
