(yellow) Alcohols

Question 1

waht are alcohols at room tempreture

Answer 1

liquid

Question 2

Why are alcohols less volatile than the corresponding alkane?

Answer 2

OH, hydroxyl group can make H-bonds between adjacent molecules.

These are stronger than the London forces between alkanes

So more heat energy is required to overcome them, leading to higher B Pts.

Question 3

Explain why hydrogen bonding accounts for the fact that methanol, at room temperature, is a liquid that mixes freely with water, while ethane is a gas which is insoluble in water.

Answer 3

Both have similar number of electrons and London forces

Methanol can form H-bonds with water so mixing with it.

Ethane can only form weaker London forces so cannot disrupt the H-bonds between the water molecules.

Question 4

what is the definition of a elimination reaction

Answer 4

Elimination reaction is the removal of one or more groups or atoms from adjacent C atoms forming an unsaturated molecule.

Question 5

what is the definition of a dehydration reaction

Answer 5

Dehydration is the removal of a water molecule – water is the only inorganic product formed in the reaction

Question 6

how do you go from an alcohol to a alkene

Answer 6

conc phosphoric acid / H2SO4 (catalyst)

this forms an alkene + water

Question 7

what is the definition of nucleophile

Answer 7

Nucleophile
An electron rich species with an available lone pair of electrons
May be negatively charged
Reacts by donating a pair of electrons to form a new covalent bond to a carbon atom.

Question 8

what is the definition of a substitution reaction

Answer 8

Substitution reaction
Where one group replaces another in a molecule e.g. when an alcohol forms a chloroalkane . OH group is replaced by Cl atom

Question 9

how do you go from an alcohol to a chloro alkane
give reagents and conditions

Answer 9

PCl5

R-OH + PCl5 —-> R-Cl + POCl3 + HCl

or HCl

Question 10

how do you go from alcohol to bromoalkane
give reagengts and conditions

Answer 10

heat under reflux
conc H2SO4
conc KBr
which produces HBr in situ

KBr + H2SO4 —> HBr + KHSO4

HBr + CH3CH3CH2OH —> CH3CH3CH2Br + H2O

propanol as an example

Question 11

how do you go from an alcohol to an iodine alkane

give reagents and conditions

Answer 11

moist red phosphorus and iodine this produces PI3 in situ

3 CH3OH + PI3 —-> 3 CH3I + H3PO3

heat under reflux

Question 12

what is the colour change when you reduce chromium from +6 to +3

Answer 12

orange to green

Question 13

how do you know if a reaction has taken place in a oxidation potassium dichromate reaction

Answer 13

the colour of the solution has turned from orange to green

Question 14

how do you oxidise alcohols

give reagents and conditions

Answer 14

reagents K2Cr2O7

H2SO4

reflux / disstilation

orange to green

Question 15

what is the pecie of aparatus called that connects the tap funnel, condensor and pear shaped flask together in distilation

Answer 15

still head

Question 16

some water may be lest behind after drying name some drying agents

Answer 16

silica

CaSO4
MgSO4
Na2SO4

Question 17

what is the idea filtering funnel

Answer 17

1) Solvent extraction

* A separating funnel is used, the reaction mixture is put into this and another solvent which is immiscible (insoluble) in the reaction mixture, so two layers are seen.

* The desired product must also be more soluble in the new solvent added

* The idea is that the product will move into the new solvent and any impurities will remain behind in the original reaction mixture.

* Then the two layers are ‘tapped off’ and the desired layer kept.

alcohols soluable in water while other organics are not