Alcohols

Question 1

general formula of alcohols

Answer 1

CnH2n+1OH

Question 2

describe a primary alcohol

Answer 2

one carbon is bonded to the carbon on the OH group

Question 3

describe a secondary alcohol

Answer 3

two carbons are bonded to the carbon on the OH group

Question 4

describe a tertiary alcohol

Answer 4

three carbons are bonded to the carbon on the OH group

Question 5

general equation for reaction with oxygen (combustion)

Answer 5

ROH + O2 –> CO2 + H2O

Question 6

what type of reaction is reactions with halogenoalkanes

Answer 6

substitution

Question 7

Alcohol + phosphorus pentachloride –>

Answer 7

chloroalkane

Question 8

general equation for reaction with phosphorus pentachloride (secondary + primary alcohols)

Answer 8

ROH + PCl5 –> RCl + HCl + POCl3

Question 9

alcohol + hydrochloric acid –>

Answer 9

chloroalkane

Question 10

general equation for reaction with hydrochloric acid (tertiary alcohols)

Answer 10

ROH + HCl –> RCl + H2O

Question 11

alcohol + bromine ions –>

Answer 11

bromoalkane

Question 12

conditions for reaction with bromine ions

Answer 12

• 50% concentrated H2SO4
  (acid catalyst)

Question 13

equations for reaction with bromine ions

Answer 13

KBr + H2SO4 –> HBr + KHSO4
ROH + HBr –> RBr + H2O

Question 14

Alcohol + phosphorus triiodide –>

Answer 14

iodoalkane

Question 15

equation for making phosphorus triiodide

Answer 15

2P + 3I2 –> 2PI3
(red phosphorus + iodine)

Question 16

general equation for reaction with phosphorus triiodide

Answer 16

3ROH + PI3 –> 3RI + H3PO3

Question 17

name of H3PO3

Answer 17

phosphonic acid

Question 18

what type of reaction forms alkenes

Answer 18

elimination

Question 19

what is needed for an elimination reaction

Answer 19

• concentrated acid catalyst
  (concentrated phosphoric acid- H3PO4)

Question 20

reaction of ethanol mixed with concentrated phosphoric acid

Answer 20

C2H5OH –> CH2=CH2 + H20

Question 21

what products are formed in the reaction with conc phosphoric acid

Answer 21

two possible alkenes, depending on what side of the hydroxyl group the Hydrogen is eliminated from

Question 22

how is the reaction with PCl5 a test for alcohols

Answer 22

produces white, steamy fumes that can turn damp blue litmus paper red

Question 23

which types of alcohols can be easily oxidised

Answer 23

primary and secondary

Question 24

name an oxidising agent

Answer 24

acidified potassium dichromate (VI)

Question 25

what are primary alcohols oxidised to (with initial heating)

Answer 25

aldehydes

Question 26

what are primary alcohols oxidised to under reflux

Answer 26

carboxylic acids

Question 27

equation for oxidation of ethanol (heating)

Answer 27

CH3CH3OH + [O] --> CH3CHO + H2O -------------------------------ethanal----------

Question 28

equation for reflux of ethanol

Answer 28

CH3CHO + [O] --> CH3COOH

Question 29

what are secondary alcohols oxidised to produce

Answer 29

ketones

Question 30

ethan-2-ol oxidisation equation

Answer 30

CH3CH(OH)CH3 --> CH3CH3CO + H2

Question 31

potassium dichromate formula

Answer 31

K2Cr2O2

Question 32

what is potassium dichromate

Answer 32

an oxidising agent (is reduced when an alcohol oxidises)

Question 33

colour change of K2Cr2O2 when primary + secondary alcohol oxidised

Answer 33

orange - green

Question 34

colour change of K2Cr2O2 when tertiary alcohol oxidised

Answer 34

orange - orange (no colour change)

Question 35

what is used to test for aldehydes

Answer 35

benedics/fehlings solution

Question 36

describe how to use fehlings solution

Answer 36

add a few drops of solution to a gently warmed test tube containing the solution - if aldehyde present a red precipitate will form

Question 37

what occurs in a negative result in fehlings test

Answer 37

solution stays blue (Ketones will produce a negative result)

Question 38

use of heating under reflux

Answer 38

allows reactions such as oxidation of primary alcohols all the way to formation of carboxylic acids

Question 39

use of reflux condenser

Answer 39

ensures vapours condense and return to flask for further heating- product vapours don't escape

Question 40

role of separating funnel

Answer 40

separate two liquids of different densities

Question 41

how does a separating funnel work

Answer 41

mixture is added, liquid will separate into two layers depending on their different densities (more dense liquid will be found at the bottom) - open tap to remove denser liquid into a different flask

Question 42

role of distillation

Answer 42

separate liquids with different boiling points

Question 43

how does distillation work

Answer 43

- pear shaped flask heated, liquid with lower boiling point evaporates first - vapour rises up flask into tubes - condenser causes it to cool and condense into a liquid - is then collected in a separate flask

Question 44

how do you dry compounds

Answer 44

addition of anhydrous salts

Question 45

how does drying work

Answer 45

absorbs moisture and water present, drying and purifying the compound

Question 46

name a common anhydrous salt

Answer 46

sodium sulphate

Question 47

how do you test the purity of a substance

Answer 47

boiling point determination

Question 48

what kind of boiling point does a purer substance have

Answer 48

a closer boiling point to that of the database boiling point value

Question 49

how do you determine a substances boiling point

Answer 49

- place into a thiele tube containing inverted capillary tube - substance is heated above its boiling point, it then cools and condenses back into a liquid - it is then drawn into the capillary tube (the temperature at which the change occurs is its boiling point)