redox

Question 1

what is oxidation

Answer 1

loss of electrons

Question 2

what is reduction

Answer 2

gain of electrons

(lowers oxidation state)

Question 3

what is an oxidation state

Answer 3

indicator of degree of oxidation of an atom in a compound

Question 4

what is the sum of all oxidation states in a neutral molecule

Answer 4

zero

Question 5

what is the oxidation state of a free uncombined element

Answer 5

zero

Question 6

what is the oxidation state of a simple ion

Answer 6

oxidation state would be equal to the net charge on the ion

Question 7

name some reducing agents

Answer 7

NaBH4, sodium cyanoborohydride, lithium aluminium hydride, hydrogen, metals

Question 8

name chemicals that reduce esters and say if theyre good at reducing or not

Answer 8

LiAlH4 (lithium aluminium hydride)- best

NaBH4- reduces esters slowly

NaCNBH3 (sodium cyanoborohydride) - doesnt reduce at all

Question 9

describe reduction mechanism using NaBH4 (idk if need)

Answer 9

BH4 ion gives H to molecules =o, o-, o- attacks H+ to give OH

Question 10

why not use LiAlH4 for every reduction

Answer 10

rule is to use the mildest conditions for a reaction to prevent unwanted side reactions and more reactive reagents are harder to handle usually

Question 11

describe the mechanism of reduction of esters

Answer 11

addition elimination, reducing agent used twice

Question 12

how to stop reduction of esters after the formation of an aldehyde to stop it forming alcohol

Answer 12

use reagent called DIBAL (diisobutyl aluminium hydride/ iBU2ALH)

Question 13

what does the reduction of ester make

Answer 13

alcohol (aldehyde as a middle step)

Question 14

what are imines

Answer 14

double bond N

Question 15

what is NaCNBH4

Answer 15

sodium cyanoborohydride

Question 16

what is NaBH4

Answer 16

sodium borohydride

Question 17

what is iBu2ALH

Answer 17

DIBAL/ diisobutyl aluminium hydride

Question 18

what is LiAlH4

Answer 18

lithium aluminium hydride

Question 19

will NaCNBH4 reduce esters? aldehydes/ketones? imines?

Answer 19

esters= no
aldehydes/ketones= slowly
imines= yes

Question 20

will NaBH4 reduce esters? aldehydes/ketones? imines?

Answer 20

esters= slowly
aldehydes/ketones= yes
imines= yes

Question 21

will iBu2AlH reduce esters? aldehydes/ketones? imines?

Answer 21

esters= yes but stops at aldehyde
aldehydes/ketones= no
imines= yes

Question 22

will LiAlH4 reduce esters? aldehydes/ketones? imines?

Answer 22

esters= yes, all the way to alcohol
aldehydes/ketones= yes
imines= yes

Question 23

describe the mechanism for hydrogenation

Answer 23

on a catalytic surface, uses ethene and creates ethane in the end

Question 24

what does the reduction of alkynes make

Answer 24

alkenes then alkanes

Question 25

how to stop the reduction of alkynes at the alkene step

Answer 25

use palladium, poisons catalyst with lead to reduce activity and get selectivity

Question 26

name some hydrogenation reactions

Answer 26

reduction of benzene to cyclohexane aromatic nitro to amine (NO2>NH2) removal of benzyl group (remove benzene)

Question 27

name 3 ways to achieve oxidation

Answer 27

high oxidation state metals (manganese+7/chromium +6), halogens and hypervalent halogens (chlorine, bromin, NaIO4), oxygen 0 or -1 substances (h2o2, o2, o3)

Question 28

what are the products of oxidising alcohols

Answer 28

primary- aldehyde, carboxylic acid secondary- ketone tertiary- doesnt oxidise, lack of reactive C-H bonds

Question 29

how to stop the oxidation of primary alcohols at aldehyde step

Answer 29

use PCC (pyridinium chlorochromate), PCC in dichloromethane will oxidse primary alcohols to aldehydes

Question 30

what metals are usually used for hydrogenation

Answer 30

platinum, nickel, palladium