Organic: Halogenalkanes

Question 1

what type of bonds do halogen alkenes contain

Answer 1

polar bonds due to highly electronegativity in the halogen compared to the carbon, causing a difference in electronegativity

Question 2

give the uses for halogenalkanes

Answer 2

refrigerants -CFCs bad for environment
solvants

Question 3

explain the classification of halogen alkanes H
H-C-Cl
H

Answer 3

primary- contains 1 R group
secondary- contains 2 R groups
tertiary- contains 3 R group

Question 4

explain why halogenalkanes have boiling points than alkanes/alkenes even with the same molecular mass

Answer 4

they contain dipoles due to different electronegativity so the force of attraction between molecules are stronger than VdW forces in alkenes/alkanes so more energy is required to overcome

Question 5

explain why the boiling point increases as we go down the halogen group

Answer 5

going down the group the molecule becomes larger so there are more e- meaning stronger VdW force/ increase in size so more energy is required to break down going down group 7

Question 6

are halorgenalkanes soluble or not

Answer 6

they are not soluble since not polar enough to dissolve in water since they are not able to form hydrogen bonds with water and wont break dipole dipole and vdw forces of attraction

Question 7

what doesa. curly arrow represent

Answer 7

the movement of a pair of electrons

Question 8

where do arrows always start at in a mechanism

Answer 8

either, a lone pair or from the middle of a bond

Question 9

if you make a bond

Answer 9

you must break a bond

Question 10

give common examples of nucleophiles

Answer 10

OH- CN- NH3

Question 11

why do we ignore the metals associated with nucleophiles

Answer 11

they are spectator ions

Question 12

define a nucleophile

Answer 12

a species attracted to a positive by donating an electron pair

Question 13

what two factors effect the rate of reaction of halogenalkanes

Answer 13

strength of the bond enthalpy
number of alkyl groups attracted to the c-x bond

Question 14

which c-x bonds will have the slowest or fastest reaction rate

Answer 14

c-f has 484 bond enthalpy adn c-i has 238 bond enthalpy
going down the halogen group, the energy required to overcome the bonds decreases
so iodomethane will have the fastest reaction rate because the c-i bond is the weakest, less energy to overcome

Question 15

Reactivity, rate, bond strength: rate the halogens going down the group

Answer 15

reactivity increasings
rate increases
bond strength decreases

Question 16

give the two reactions that halogenalkanes undergo

Answer 16

nucleophilic substitution- A halogen atom is substituted by another atom or group of atoms forming alcohols, nitriles and amines.

elimination reactions- hydrogen halide is eliminated during the reaction and an alkene is produced

Question 17

during elimination reaction using KOH what are the condiotions

Answer 17

hot concentrated and dissolved in ethanol

Question 18

where does the elimination arriw go to

Answer 18

always from carbon which is next to the carbon that is bonded to halogen

Question 19

aqueous conditions —- alcohol

Answer 19

OH- acts as a nucleophile donating ena electron pair SUBSTITUTION H-C-C-OH

Question 20

anyhydrous conditions —- alkene

Answer 20

OH- acts as a base, accepts a H+ to form h20 ELIMINATION H-C=C-H

Question 21

How do halogenoalkanes cause depletion of the ozone layer

Answer 21

Due to the strength of c-cl and c-f bonds its very unreactive, toxic and volatile, but the CFS undergo reactions of chlorine radicals with the ozone, decomposition atmosphere with UV radiation
CFC are volatile so if escaped they evaporate into atmosphere/stratosphere with more UV radiation exposed, forming more radicals

Question 22

give the equations for ozone decomposition

Answer 22

Propagation step 1: Cl* + O3 → ClO* + O2

Propagation step 2: ClO* + O3 → 2O2 + Cl*

Overall equation: 2O3 → 3O2

Question 23

scientists have found that using CH2F2, CHF3, C2H2F4 compounds wont threat ozone layer

Answer 23

they do not contain Cl so clorine radicals cannot form

Question 24

define
halogenalkanes
nucleophilic reaction
elimination reaction
hydrolysis

Answer 24

Halogenoalkanes - a family of compounds that have had one or more hydrogen atoms in an alkane replaced by a halogen atom (these are also referred to as haloalkanes by some exam boards and some resources refer to them as alkyl halides)
Nucleophilic substitution - a reaction in which an electron-rich nucleophile displaces another atom or group of atoms
Elimination reaction - a reaction which involves the removal of a small molecule from one reactant molecule and produces two products
Hydrolysis - a reaction that involves water (or the aqueous solution of a hydroxide) that results in the breaking of a bond and the formation of two products