Reactivity 3.4 Flashcards
(16 cards)
Nucleophile
A reactant that forms a bond to its reaction partner by donating both bonding electrons
Charge of a nucleophile
Can be neutral (one or more pairs of non-bonding electrons like water) or negative ions that contain at least one pair of non-bonding electrons (ie cyanide or hydroxide)
Electrophile
A reactant that forms a bond to its reaction partner by accepting both bonding electrons
Charge of a electrophile
Can be neutral (such as AlCl which is electron deficient as there is only three central electrons) or positively charged ions such as H+
Which is more reactive - alkanes or halogenoalkanes?
Halogenoalkanes (with the exception of fluoroalkanes) as the C-Cl/Br/I bonds are weaker than C-H/C
Why are flouroalkanes unreactive?
Because their C-F bonds are very strong
Main reaction of halogenoalkanes
Nucleophilic substitution
General equation for the reaction of halogenoalkanes
RX + OH- -> ROH + X- (carbon halogen bond in the molecule is polar due to differences in electronegativity)
What happens during a nucleophilic substitution reaction?
Carbon atom becomes electron deficient with a small positive charge and the halogen atom has a small negative charge. OH has a non-bonding pair of electrons and is attracted to the carbon atom (+) which breaks the C-X bond heterolytically and the halide ion leaves.
What acts as the nucleophile during a nucleophilic substitution reaction?
The hydroxide ion which contains the non-bonding pair
What acts as the electrophile during a nucleophilic substitution reaction?
The halogenoalkane due to the C+
Leaving group
The halogen which leaves as a halide ion
What does a curly arrow show you?
Tail of the arrow is the initial location of the electron pair and the head of the arrow is where the electron pair has moved.
Mechanisms that addition reactions of alkenes can proceed through
- Adsorption reaction catalysed by transition metals
- Addition polymerisation catalysed by addition of peroxides
Why are electrophiles attracted to alkenes?
The double bond has a high electron density so electrophiles can add across the double bond.
How can bromine water be used to distinguish between saturated and unsaturated compounds?
