orgo lab quiz

Question 1

why can’t alkanes be used as starting materials to make compounds?

Answer 1

alkanes are unreactive because:
-they are very stable
-very consistent electron density
-they don’t have a functional group
-they are sp3 hybridized

Question 2

functional groups are the center of…

Answer 2

reactivity

Question 3

what mechanism can alkanes react with?

Answer 3

free radical mechanism

Question 4

what are the steps of the free radical mechanism?

Answer 4

1. initiation
2. propagation
3. termination

Question 5

what happens during the initiation step?

Answer 5

you have a halogen and you need energy that overcomes the bond association energy inside the bromine molecule
the energy you’re applying has to be greater than or equal to the energy of the bond, so it will break in the middle. this is called hemolytic
homolytic bond cleavage
(you are generating the radicals, concentration of the radical goes up)

Question 6

describe what happens during the propagation step

Answer 6

you are maintaining the concentration of the radical (you start with one Br radical and you end up with one Br radical)

Question 7

termination

Answer 7

the radicals combine with each other
concentration of radicals goes down

Question 8

how many steps are there in the free radical mechanism?

Answer 8

six steps (draw out all six for the quiz)

Question 9

what applies to the stability of the radical?

Answer 9

-resonance
-hyperconjugation

Question 10

what type of hydrogens are in cyclohexane?

Answer 10

secondary aliphatic (1 kind of hydrogen)

Question 11

what is a mono-halogenated product?

Answer 11

we only want to halogenate one hydrogen

Question 12

what is a limiting reagent?

Answer 12

the reactant that gets consumed first in a chemical reaction and therefore limits how much product can be formed.

Question 13

the trend under light condition and dark condition is the…

Answer 13

same

Question 14

why does the reaction under light condition take faster?

Answer 14

because you are applying energy to break the bond in the molecular bromine homolytically

Question 15

what is the limiting reagent?

Answer 15

bromine

Question 16

why don’t we watch the glassware with acetone?

Answer 16

we use dichloromethane instead of acetone because acetone reacts with bromine and will form bromoacetone and it will make you cry

Question 17

what was the most reactive for this experiment?

Answer 17

isopropyl benzene

Question 18

what was the least reactive for this experiment?

Answer 18

tert-butyl benzene

Question 19

how do we determine the order sequence/reactivity?

Answer 19

We determined the order sequence because in the propagation step when the Br radical tries to extract a hydrogen from the hydrocarbon, it’s going to extract the most reactive hydrogen. The most reactive hydrogen is the one that’s going to form the most stable radical.

Question 20

Explain why is a 1° benzylic radical more stable than a 1° aliphatic radical

Answer 20

Benzylic radicals are more stable than aliphatic radicals because of resonance effects

Question 21

should the reaction occur under dark conditions?

Answer 21

no it shouldn’t happen at all but in reality it will because we are going to keep a little bit of light in the lab because we want to monitor the reaction

Question 22

how do we monitor the progress of the reaction?

Answer 22

by the disappear of the brown color in bromine. when the brown color goes away the reaction in complete

Question 23

On the basis order of stability of the radicals deduce the order of reactivity toward the radical bromination of the seven different types of hydrogens: (1) 1o aliphatic, (2) 2o aliphatic, (3) 3o aliphatic, (4) 1o benzylic, (5) 2o benzylic, (6) 3o benzylic, and (7) aromatic.

Answer 23

Most to least reactive:
3° benzylic, 2° benzylic, 1° benzylic, 3° aliphatic, 2° aliphatic, 1° aliphatic, aromatic

Question 24

when you have two acids reacting with each other what happens?

Answer 24

the stronger acid acts as an acid the weaker acid acts like a base

Question 25

what is the strong and weak acid in the EAS experiment?

Answer 25

strong: sulfuric acid
weak: nitric acid ?

Question 25

what is the strong and weak acid in the EAS experiment?

Question 26

why will very little meta product form?

Answer 26

because Br are ortho/para directors they are electron donating group
the stability of the cation or the positively charged resonance