4.2 alcohols, haloalkanes and analysis

Question 1

alcohols

Answer 1

All alcohols contain a carbon atom bonded to a hydroxyl group, C-OH

Question 2

primary alcohols

Answer 2

The carbon bonded to the –OH group is bonded to 1 carbon atom

Question 3

secondary alcohols

Answer 3

The carbon bonded to the –OH group is bonded to 2 carbon atoms

Question 4

tertiary alcohols

Answer 4

The carbon bonded to the –OH group is bonded to 3 carbon atoms

Question 5

combustion of alcohols

Answer 5

Alcohols burn to produce carbon dioxide and water. The reactions are exothermic, releasing large amounts of energy.
CH3OH + 1 ½ O2 → CO2 + 2H2O
C2H5OH + 3O2 → 2CO2 + 3H2O

Question 6

oxidation of alcohols

Answer 6

Primary alcohols can be oxidised to produce either a aldehyde, or a carboxylic acid.
secondary alcohols can be oxidised to form ketones
Tertiary alcohols don’t undergo oxidation

Question 7

what must occur for oxidation to occur

Answer 7

Oxidation of an alcohol can only occur if the C bonded to the OH is also bonded to at least 1 hydrogen atom.

Question 8

what is the most common oxidising agent

Answer 8

Most common oxidising agent is acidified solution of potassium dichromate. The acidified dichromate (VI), is a bright orange solution which turns a dark green when an alcohol is oxidised.
[O] represents the oxidising agent.

Question 9

elimination of alcohols

Answer 9

When reacted with hot, concentrated sulfuric acid or hot aluminium oxide ( Al2O3), an alcohol is dehydrated to form an alkene.

Question 10

physical properties of alcohols

Answer 10

The simplest alcohols are liquid at room temperature and are miscible with water
Has a relatively high boiling and melting points due to hydrogen bonds that form between the lone pair of electrons on the oxygen of the –OH group in 1 molecule and hydrogen in the adjacent alcohol molecule
When boiled or melted, energy is required to break the intermolecular forces

Question 11

what is the bonding and intermolecular forces of alcohols

Answer 11

Has induced dipole-dipole interactions to help bind it together
Also has hydrogen bonds

Question 12

what is haloalkanes

Answer 12

A compound in which 1 or more hydrogen atoms of an alkane are replaced by a halogen atom, if 1 hydrogen is replaced, then the general formula is CnH2n+1X ( where X is F, CL, Br or I)
Are subdivided into primary, secondary and tertiary

Question 13

what is the rates of reactions of haloalkanes (slowest to fastest)

Answer 13

React with the same reagents but the rate of which they react is different.
The rate of reaction depends on the strength of the C-X bond.
Tertiary haloalkanes react the fastest and primary haloalkanes react the slowest. This indicates that the C-X bond in tertiary haloalkanes is the weakest

Question 14

primary haloalkanes

Answer 14

The carbon bonded to the –halogen is bonded to 1 carbon atom

Question 15

secondary haloalkanes

Answer 15

The carbon bonded to the halogen is bonded to 2 carbon atoms

Question 16

tertiary haloalkanes

Answer 16

The carbon bonded to the halogen is bonded to 3 carbon atoms

Question 17

haloalkane reactivity

Answer 17

when reacted under identical conditions,
1- iodobutane reacts the fastest and 1-chlorobutane reacts the slowest.
C-I bond is the weakest and the least amount of energy is required to break it. C-F bond is so strong it rarely undergoes hydrolysis.

Question 18

hydrolysis of haloalkanes in a substitution reaction

Answer 18

Hydrolysis of haloalkanes using water is very slow and results in the replacement of the halogen with –OH groups to form alcohols.
Much quicker in the presence of an alkali catalyst :OH-. When a primary alcohol is heated under reflux with an aqueous solution of an alkali, the haloalkane is hydrolysed to a primary alcohol

Question 19

hydrolysis of haloalkanes conditions

Answer 19

Reagent - sodium ( or potassium) hydroxide ( a alkali is required)
Conditions - solvent must be water and reaction mixture must be heated under reflux
Equation - CH3CH2Br+ NaOH → CH3CH2OH

Question 20

primary haloalkane nucleophilic substitution

Answer 20

Nucleophile- an ion/molecule that is an electron pair donor.
R-X + :Nu- → R-Nu +:X-

Question 21

synthetic routes

Question 22

infrared spec

Answer 22

Infrared radiation causes covalent bonds to vibrate and particular bonds respond at different frequencies ( energies).
The frequency at which they vibrate is the absorptions of that bond

Question 23

mass spec

Answer 23

Shows a peak for each isotope of that element.
Shows multiple peaks, the peak with the highest m/z value, the molecular ion shows the relative molecular mass of the molecule. The rest of the peaks show fragment ions formed when the molecule breaks up.
You can work out the empirical formula from the mass spectra