quiz material

Question 1

what is a feature of carbenes

Answer 1

neutral, regiospecific

Question 2

what do carbenes make

Answer 2

cyclopropane

Question 3

through what does the Simmons smith reaction form a cyclopropane

Answer 3

it will form a carbenoid which acts like a carbene

Question 4

what is a radical

Answer 4

any atom with an unpaired electron

Question 5

to make a radical, what do you need to do?

Answer 5

you need to put in energy, radicals are high in energy and are unstable

Question 6

what are the three steps involving radical reactions

Answer 6

initiation, propagation, termination

Question 7

what are the three ways to make a radical, what is this step called?

Answer 7

1) Halogen (Cl2,Br2) with heat or light

2) Organic peroxide (ROOR) with heat or light

3) AIBN Azoisobutyronitrile

this is an initiation step

Question 8

why is H2O2 in a dark bottle

Answer 8

itll break down into radicals, a similar process occurs with ROOR

Question 9

how do we characterize the bond between Cl-Cl and RO-OR

Answer 9

weak bonds, when subjected to light they homolytically cleave to form radicals

Question 10

what forms when we react ROOR in light?

Answer 10

it forms two alkoxy radicals

Question 11

why do we like to use AIBN to form radicals?

Answer 11

ROOR is toxic, Cl2 is a gas, Br2 is a liquid and are hard to work with

Question 12

what is AIBN

Answer 12

it is a radical initiator that is solid and easy to work with

Question 13

why do we like to use AIBN

Answer 13

it forms 2 radicals and N2 bubbles off in solution, this pushes the reaction towards products since its continously losing nitrogen gas

Question 14

what is the intitiation step

Answer 14

it is the formation of a radical through the use of heat or light

Question 15

what is a radical halogenation

Answer 15

A halogen atom replaces one or more of the hydrogen atoms of the alkane, and the corresponding hydrogen halide is formed as a by-product

Question 16

what is a propagation step

Answer 16

it describes the chain reaction of radical formation. Where the presence of one radical reacts with other stable molecules to form more free radicals

Question 17

what is the first step in radical hydrogenation of Cl2 and methane?

Answer 17

initiation, the Cl-Cl will homolytically cleave in the presence of light or heat

Question 18

what is the second step in radical hydrogenation

Answer 18

the radical Cl reacts with the methyl to create an HCl byproduct and a methyl radical

Question 19

what is the second part of the propagation step of radical hydrogenation of Cl2 and methane?

Answer 19

the radical methyl will react with a new Cl-Cl molecule and form methyl chloride and a new Cl radical (propagation step, it can be reused)

Question 20

when does propagation stop?

Answer 20

when we stop supplying the reaction with starting material

Question 21

what is the termination step

Answer 21

it is when we stop supplying the reaction with starting materials, any radical byproducts can now collide and form bonds together to create unfavorable products

Question 22

what is a termination step

Answer 22

The termination steps actually reduce the number of radicals by consuming radicals, but not producing any.

Question 23

if you have a reaction that only forms radicals, what step is it?

Answer 23

it is a initiation step

Question 24

if you have a reaction that forms products AND radicals, what step is it?

Answer 24

it is a propagations step

Question 25

if you have a radical reaction that forms no new radicals, what step is it?

Answer 25

it is a termination step

Question 26

what is a disadvantage of radical halogenation with CH3 with Cl2

Answer 26

we keep removing halogens until we reach a fully replaced carbon tetrachloride molecule

it creates a mixture of products 1,2,3

Question 27

what is an advantage of radical halogenation

Answer 27

it increases the functionality by transforming a unreactive alkane to a reactive alkyl halide

Question 28

what is the order of stability for radicals?

Answer 28

3°>2°>1° due to the inductive effect

Question 29

why is the benzyllic radical stable

Answer 29

it is stabilized by resonance