Haloalkanes and Alkenes Flashcards Preview

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Flashcards in Haloalkanes and Alkenes Deck (48):
1

How many H atoms are bonded to the C of a primary haloalkane?

2

2

How many H atoms are bonded to the C of a secondary haloalkane?

1

3

How many H atoms are bonded to the C of a tertiary haloalkane?

0

4

Define nucleophillic substitution in terms of a heloalkane

halide substituted by nucleophile

5

define nucleophile

an electron pair donor, electron rich so attracted to areas of low electron density

6

equation and conditions for a nucleophilic rection with OH- ions

Haloalkane + OH- → alcohol + halide ion
conditions: warmed with OH-(aq)

7

equation and conditions for a nucleophilic reaction with cyanide ions

haloalkane + CN- → nitrile + halide ion
conditions: warmed under reflux, alkane (aq) in h2o + alcohol

8

equation for nitrile rection following nucleophilic substitution

nitrile + HX + h2o → carboxylic acid + ammonium halide

9

equation and conditions for nucleophilic reaction with excess ammonia

haloalkane + 2NH3 → amine + ammonium halide
conditions: heat in a sealed copper tube

10

why does NH3 act as a nucleophile

bc the N has a lone pair of electrons

11

how would you encourage the reaction to cease after amine and ammonium halide production?

limit NH3 to only 2NH3, and the 1st would break the C-X bond and the 2nd makes the N+ neutral

12

how would you monitor the production of X- in nucleophilic reactions

add AgNO3 (acidifed with HNO3), presence of a halide would see a ppt formed.
Cl- white ppt of AgCl → redissolves with dilute NH3
Br- cream ppt of AgBr → redissolves with conc. NH3
I- yellow ppt of AgI → no redissolving

13

how would you compare reactivities of halogens?

same vold of haloalkane in 3 tubes, same vol or C2H5 and vol+conc of AgNO3. time how long for a cross under conical flask to disappear with ppt covering it
bond strength outweighs electronegativity
C-I has lowest b.strength so yellow ppt forms first

14

equation and conditions for elimination reaction with alcoholic OH-

haloalkane + OH- → alkene + h2o + X-
conditions: hot alcoholic OH-

15

outline the elimination OH- mechanism

OH- attacks H on C next-door to the C with the X on it
product depend on which side the OH eliminates from (uncontrallable)

16

why does OH behave as a nucloephile

O has a lone pair of electrons and so donates a pair to the C to form a new covalent bond

17

why does OH behave as a base

O lone pair forms new bond with H+ neutralising the substance

18

solvent, temperature and type of haloalkane encouraging nucleophilic substitution

h2o, low temp, 1°→2°→3°

19

solvent, temperature and type of haloalkane encouraging elimination reaction

alcohol, high temp, 3°→2°→1°

20

define CFC's

chloroflorocarbons, all H atoms replaced by Cl or F
unreactive as C-Cl and C-F have high strength

21

CFC undergoing homolytic fission

CF2Cl2 → Cl· + CF2Cl·
UV

22

define O3

allotrope of O2, pale blue gas, absorbs harmful UV rays

23

ozone UV reactions

O2 → 2O·
UV
O· + O2 → O3
O3 → O2 + O·
UV

24

why are HFC's better than CFC's

C-F bond stronger than C-Cl bond so needs more energy to break and so less likely to break

25

Cl· acting as a catalyst for ozone absorption of UV

Cl· + O3 → O2 + ClO·
ClO· + O3 → Cl· + 2O2

overall = 2O3 → 3O2

26

general formula for alkenes

C2H2n

27

define unsaturated

contains one or more C=C double bonds

28

bonding in alkenes

>120 between C=C and the bonds (or H) of the C, <120 between the two bonds off the C.
C=C is more electron dense and so pushes the bonds futhur away from itself

29

which bond breaks first during an addition reaction

π breaks first as the σ is stronger as the orbital overlap head on creating a stronger bond

30

define a π bond

2 atomic orbital overlap side on

31

describe the trend in BP's as alkenes get longer

increase as get longer as more contact points so more VDW's need overcoming so more energy is required to overcome those

32

define an addition reaction

2 substances reacting together to form 1 product, must possess a double bond to undergo addition

33

outline an addition reaction

electron rich area attacks electron deficient area, X-X made into a more permenant dipole as it approaches the electron rich C=C bond and so the electrons in the X-X get repellled away from the C=C

34

equation for the addition reaction with halogens

alkene + halogen → dihaloalkane

35

describe observations when adding Br2 to an alkene

colour change from orange/brown to colourless as the Br2 dissolves and undergoes addition

36

define unsymmentrical alkene

an alkene that is not equal on both sides if you cit it down the centre

37

outline markovnikovs rule

when HX is added to an unsymmetrical alkene, the H will bond to the C with the higher number of H already attached to it

38

equation for the addition reaction with conc. H2SO4

alkene + H2SO4 → alkyl hydrogen sulphate

39

equation and conditions for addition reaction with h2o

alkene + h2o → alcohol
H3PO4
conditions: 300°c, 60 to 70 atm, H3PO4 catalyst

40

outline le chateliers principle

and increase in pressure with shift the equilibrium to the side with the fewest number of moles

41

outline addition polymerisation

double bond opens up and allows the C to join up with other monomer units
π breaks allowing the C to form other σ with other monomers

42

conditions for addition polymeristaion

200°c, 2000atm, zeigler-natta catalyst

43

uses of polyethene

packaging, most common used plastic

44

uses of polypropene

carpets, fibres, injection moulding

45

define non-biodegradable

does not rot or decompose naturally

46

+ve and -ve of landfill

+ve: easy, something to do with it
-ve: habitats gone, eye-sore, pollutes soil

47

+ve and -ve of incineration

+ve: reduces waste volume, can produce electricity from buring
-ve: expensive, produces lots of CO2 and carcenogenic gases

48

+ve and -ve of recycling

+ve: reduction in use and consumption of raw materials
-ve: uses lots of energy from transport, labour intensive