Alkanes Flashcards
What is it called when an Alkane reacts with a halogen (Cl2, F2, Br2)
A haloalkane
Examples of haloalkanes
1,2 dibromobutane
1,1,1 tribromo 2,2,2 trichloroethane
What is a chemical mechanism
Shows the movement of electrons during a reaction and can help us understand why certain products are formed instead of others.
What’s it called if electrons move singly
A free radical mechanism is happening
If electrons move in pairs what type of mechanism is it
Polar mechanism is formed
What is a free radical
An atom , molecule , or ion that has unpaired valence electrons in the outer shell
What’s formed during homolytic fission
Free radicals are formed, in which two electrons in a covalent bond are returned to the atoms from which they originated during covalent bond formation.
What is the homolytic reaction the reverse of
Reverse of covalent bond formation
What do free radicals contain
Unpaired electrons and have no charge
What does the fish hook arrow represent
Represents the movement of one electron ie the electrons move singly
Why are free radicals very reactive
They no longer have full outer shells and will react with many species in order to regain a full outer shell.
How is an alkane turned into a haloalkane
Free radical substitution mechanism
Involves free radicals the substitution part refers to the swapping of an H atom by a halogen atom as shown by the overall reaction of methane with chlorine eg CH4+Cl2->CH3Cl+HCl
What’s the first step in the mechanism
Initiation, UV light can split the Cl2 molecule to make free radicals
Cl2-> 2Cl .
What is step 2 in the mechanism
Propagation - free radicals are used up, products are formed and more free radicals are regenerated
Radical + molecule -> different radical + different molecule
CH4 + Cl. -> CH3 + HCl
What is the third step
Termination, two free radicals colliding will cancel each other out and form a stable molecule
Cl. + CH3 -> CH3Cl
Cl. +Cl.-> Cl2
