Functional Group Chemistry

Question 1

what does ADME stand for?

Answer 1

absorption, distribution, metabolism, excretion

Question 2

name 4 features of a nucleophile

Answer 2

• nucleus-loving
• electron rich
• negative charge/lone pair of electrons
• double bonds

Question 3

name 3 features of an electrophile

Answer 3

• electron-loving
• electron poor
• positive charge

Question 4

what are leaving groups?

Answer 4

terminology used for ions or neutral molecules that are displaced from a reactant as part of a mechanistic sequence

Question 5

how are leaving groups formed?

Answer 5

a consequence of a nucleophile attacking an electrophile, where the electrophile carries a suitable leaving group

Question 6

what makes a good leaving group?

Answer 6

those that form stable ions or neutral molecules after they leave the substrate

Question 7

what is heterolysis?

Answer 7

bond breaks such that both of the electrons stay with one of the atoms

Question 8

what is homolysis?

Answer 8

bond breaks so that each of the atoms retains one of the bonding electrons

Question 9

what is standard free energy?

Answer 9

the different energy levels between the reactants and the products

Question 10

what is activation energy?

Answer 10

the energy difference between the starting material and the transition state

Question 11

what happens to the boiling point of alkanes as molecular weight increases?

Answer 11

it increases

Question 12

what are the ONLY intermolecular forces present in alkanes?

Answer 12

weak London forces

Question 13

are alkanes reactive or unreactive?

Answer 13

unreactive

Question 14

what do alkanes produce during combustion?

Answer 14

CO2, H2O and heat

Question 15

during halogenation, what do alkanes react with?

Answer 15

chlorine and bromine

Question 16

when can halogenation occur?

Answer 16

• at high temperatures

- in the presence of high energy light

Question 17

what mechanism is halogenation?

Answer 17

radical mechanism

Question 18

what are the three steps in a radical mechanism?

Answer 18

• initiation
• propagation
• termination

Question 19

what happens during initiation?

Answer 19

• formation of radical

- light induced formation of chlorine radicals through homolysis from neutral chlorine

Question 20

what happens during propagation?

Answer 20

• one radical is used to generate another radical

- the chlorine radical can now abstract a hydrogen from another neutral molecule CH4 producing a methyl radical

Question 21

what happens during termination?

Answer 21

-the combination of two radicals to produce a neutral species

Question 22

what is hyperconjugation, how does it occur and what does it result in?

Answer 22

it is a stabilising interaction that occurs when the electrons in a o bond interact with an adjacent unfilled p orbital or pi orbital. it results in an extended molecular orbital that increases the stability of the system

Question 23

what two radicals are more stable than expected and why?

Answer 23

benzyl and allyl due to resonance:

• delocalisation of electrons
• partial radicals residing over several atoms instead of just one

Question 24

what is resonance used to describe?

Answer 24

electron charge and delocalisation

Question 25

why are cis isomers less stable than trans isomers?

Answer 25

there is a strain between the two larger substituents on the same side of the double bond

Question 26

are alkenes more or less reactive than alkanes?

Answer 26

much more reactive

Question 27

how are alkanes prepared? (3)

Answer 27

- cracking - dehydrohalogenation - dehydration

Question 28

what type of reactions do alkenes undergo?

Answer 28

electrophilic addition

Question 29

why do alkenes undergo electrophilic addition? (3)

Answer 29

- electrons in pi bond are accessible reactants - they are nucleophilic and react with electrophiles - electrons move from bond to electrophile

Question 30

what are the two types of addition reactions in an alkene and what do they involve?

Answer 30

- homolytic (involves radicals) | - heterolytic (involves cations)

Question 31

what is the rate limiting step in the addition of HX to an alkene?

Answer 31

carbocation formation

Question 32

why is the stability of the carbocation important?

Answer 32

it controls the overall outcome of the reaction

Question 33

what is Markovnikov's rule?

Answer 33

in an electrophilic addition to an alkene, the electrophile adds in such a way as to form the most stable intermediate

Question 34

what occurs in order to keep markovnikov's rule?

Answer 34

-reaction proceeds via the most stable carbocation -the electrophile adds to the sp2 carbon in the double bond that is the most substituted -

Question 35

what molecules add to alkenes to form markovnikov products in the absence of light or peroxide?

Answer 35

HCl, HBr, HI

Question 36

what happens in a regioselective reaction?

Answer 36

one constitutional isomer is the major, or the only, product

Question 37

what is determined by the stability of the intermediate carbocation?

Answer 37

the outcome of the product

Question 38

are alkyl groups electron donating or withdrawing?

Answer 38

electron donating (weakly)

Question 39

what is hyperconjugation

Answer 39

stabilising interaction between a p orbital and C-H o bonds on neighbouring carbons

Question 40

do alkyl groups increase or decrease the concentration of positive charge on C+

Answer 40

decrease

Question 41

in alcohols, what happens to the acidity as alkyl substitution increases? and what is this known as?

Answer 41

it decreases, known as a positive inductive effect

Question 42

in alcohols, what happens to the acidity when the number of halogen substituents increases? and what is it known as?

Answer 42

it also increases, known as a negative inductive effect

Question 43

how is ethanol produced?

Answer 43

industrially produced by fermentation of starch and grains

Question 44

what is the toxic dose of methanol?

Answer 44

100mL

Question 45

what is the toxic dose of ethanol?

Answer 45

200mL

Question 46

how are more complex alcohols prepared? (3 main methods)

Answer 46

- hydration of alkenes - hydrolysis of alkyl halides (nucleophilic sub reactions) - reduction of carbonyl compounds

Question 47

what 2 substances can reduce aldehydes and ketones? how do they work?

Answer 47

- sodium borohydride NaBH4 - lithium aluminium hydride LiAlH4 - they act as sources of hydride and as additions of H-H across C=O

Question 48

what is the only substance esters can be reduced by?

Answer 48

LiAlH4

Question 49

what is alkoxideformation?

Answer 49

reaction of alcohol with sodium metal

Question 50

are high oxidation state metal salts good oxidising agents? why?

Answer 50

yes, as they are soluble in water

Question 51

how does biological oxidation of alcohols occur in the body?

Answer 51

carried out by enzymes using NAD+ as a coenzyme

Question 52

what is the function of alcohol dehydrogenase?

Answer 52

converts alcohol to aldehyde

Question 53

what is the function of aldehyde dehydrogenase?

Answer 53

converts aldehyde to acid

Question 54

what can the process of biological oxidation be inhibited by?

Answer 54

disulfiram

Question 55

how can haloalkanes be used as anaesthetics?

Answer 55

accumulate in lipid membrane of nerve cells and interfere with transmission of nerve impulses

Question 56

does an alkane or haloalkane have higher BP?

Answer 56

haloalkane

Question 57

why do haloalkanes have higher BP than alkanes?

Answer 57

the greater polarisability of C-X bond

Question 58

how can haloalkanes be prepared? (4)

Answer 58

- free radical substitution of alkanes - electrophilic addition (H-X) to alkenes - halogenation of alkenes or alkynes - halogenation of alcohols

Question 59

what happens to the rate of reaction with a given nucleophile when the size of the haloalkane increases?

Answer 59

decreases

Question 60

what is the name of a one step Sn2 reaction mechanism?

Answer 60

concerted

Question 61

what is nucleophilicity?

Answer 61

a measure of how readily a compound is able to react with an electron-deficient atom

Question 62

what is polarisability?

Answer 62

a measure of how well a nucleophile can encroach on the orbital used for bonding in the electrophile

Question 63

what is basicity? and how is it measured?

Answer 63

a measure of how well a compound is willing to donate a lone pair of electrons to a proton. it is measured using the acid dissociation constant Ka