Chemical Reactions

Question 1

Synthesis

Answer 1

A + B -> AB

Question 2

Decomposition

Answer 2

AB -> A + B

Question 3

Single replacement

Answer 3

AB + C -> AC + B

Question 4

Double replacement

Answer 4

AB + CD -> AC + BD

Question 5

Homolysis

Answer 5

A:B -> A. + B.
Produces radicals

Question 6

Heterolysis

Answer 6

A:B -> A+ + :B-
Produces ions

Question 7

What direction do curly arrows represent the movement of electrons?

Answer 7

Site of high electron density to site of low electron density.
sigma- to sigma+

Question 8

What do full arrows represent?

Answer 8

Movement of a pair of electrons.

Question 9

What do half arrows represent?

Answer 9

Movement of one electrons.

Question 10

Where do heterolytic reactions almost always occur at?

Answer 10

Polar covalent bonds

Question 11

Where do heterolytic reactions almost always occur at?

Answer 11

Polar covalent bonds

Question 12

What do heterolytic reactions make?

Answer 12

Often assisted by the formation of a new bond to another molecule.
Y + AB -> YA + B

Question 13

What are the 5 key reaction mechanisms?

Answer 13

• Sn1 Substitution reaction
• Sn2 Substitution reaction
• Addition reactions
• Elimination reactions
• Free radical chain reactions

Question 14

What is a nucleophilic substitution reaction?

Answer 14

Replacement of one functional group/atom with another negatively charged functional group/atom.

Question 15

What is a nucleophile?

Answer 15

A chemical species that forms bonds by donating an electron pair.

Question 16

Draw the mechanism for a nucleophilic reaction

Answer 16

Slide 11 on week 4 of BIOS4006
A = nucleophile
Y = leaving group

Question 17

What is a Sn1 and Sn2 reaction?

Answer 17

Nucleophilic substitution reaction (double replacement)

Question 18

What is a Sn1 example reaction?

Answer 18

Reaction between a TERTIARY alkyl halide and NAOH - a 2 step reaction.

Question 19

What is a Sn2 example reaction?

Answer 19

Reaction between a PRIMARY alkyl halide and NAOH - a 1 step reaction.

Question 20

What is the difference between Sn1 and Sn2 reactions?

Answer 20

Sn1 = unimolecular
Sn2 = bimolecular

Question 21

Give an example of a photochemical free radical chain reaction.

Answer 21

Alkyl halide made from a hydrocarbon and halogen gas.
CH4 + Cl2 -> CH3Cl + HCl

Question 22

Describe the steps for a free radical chain reaction.

Answer 22

Initiation
Propagation
Chain termination
(check slides 23+24)

Question 23

What is a addition reaction.

Answer 23

2 or more molecules combine to make a larger molecule.

Question 24

What is an electrophilic addition reaction.

Answer 24

A reaction between an electrophile and nucleophile, adding to double or triple bonds.

Question 25

What is an electrophile?

Answer 25

An atom/molecule that forms bonds with another atom/molecule by accepting an electron pair.

Question 26

What is an carbocation?

Answer 26

Ion with a positively charged C atom

Question 27

What is step A in the first step of electrophilic addition?

Answer 27

+ charge on electrophile is attracted to electron denstiy in double bond.

Question 28

What is step B in the first step of electrophilic addition?

Answer 28

- As electrophile approaches double bond (of C=C) - Electrons in A-B bond are repelled towards B

Question 29

What is step C in the first step of electrophilic addition?

Answer 29

- Double bond breaks, and A binds to C (forming carbocation) - The two electrons in A-B bond move to B, forming B- ion

Question 30

What is step A in the second step of electrophilic addition?

Answer 30

B- ion acts as a nucleophile and attacks carbocation.

Question 31

What is step B in the second step of electrophilic addition?

Answer 31

- The lone pair of electrons on the B- ion are attracted towards the + charged C in carbocation - Causing B to bond to it

Question 32

What are the two mechanistic types for elimination reaction?

Answer 32

E1 - 2 step involving an intermediate carbocation E2 - 1 step

Question 33

What is hydrolysis?

Answer 33

Involves adding water to one large molecule to break it into multiple smaller molecules.

Question 34

What is a condensation reaction?

Answer 34

2 or more molecules combine to form a larger molecule, with simultaneous loss of a small molecule (e.g. water). Term usually reserved for reactions where new C-C bond is formed.

Question 35

What is esterification?

Answer 35

Process of combining an organic acid with an alcohol to form an ester + water. acid + alcohol -> ester + water

Question 36

OIL RIG

Answer 36

Oxidation Is Loss Reduction Is Gain

Question 37

What is the oxidation state?

Answer 37

The number of charges an atom would have in a molecle/ion if electrons were transferred completely.

Question 38

What is the oxidation number of uncombined elements?

Answer 38

0

Question 39

What is the oxidation number of oxygen (in most compunds)?

Answer 39

-2 Exception: In peroxides it is -1.

Question 40

What is the oxidation number of hydrogen (in most compounds)?

Answer 40

+1 Exception: H combined with a metal of lower electronegativity.

Question 41

What is the oxidation number of halogens?

Answer 41

-1

Question 42

What is the oxidation number of groups 1,2 and 3?

Answer 42

+1, +2 and +3

Question 43

What is the oxidation number of carbon?

Answer 43

Vary between +4 to -4.