14.2

Question 1

Alkenes will burn in air to produce _______ & _________ _________ (2)

Answer 1

water & carbon dioxide

Question 2

Why do alkenes react quickly with electrophiles? (3)

Answer 2

(1) the four electrons in the C=C dbl bond makes it a centre of high electron density
(2) electrophiles are attracted to it
(3) so it forms a bond by using 2 of the 4 electrons in the C=C dbl bond**

Question 3

TASK: draw the mechanism of the reaction between ethene & hydrogen bromide (HBr). (4)

Answer 3

mark the drawing from the textbook p. 226

Question 4

When HBr reacts with propene, 2-bromopropane OR/AND 1-bromopropane. The major product is 2-bromopropane. Why? (4)

Answer 4

(1) because alkyl groups have a tendency to release electrons (positive inductive effect)
(2) this effect tends to stabilise the positive charge on the intermediate carbocation
(3) the more alkyl groups there are attached to the carbocation, the more stable the carbocation is
(4) 2-bromopropane is formed from a secondary carbocation, while 1-bromopropane is formed from a primary carbocation

Question 5

TASK: draw the mechanism of the reaction between ethene & a bromine molecule (Br2). (4)

Answer 5

mark the drawing from the textbook p. 228

Question 6

How do you test for a C=C dbl bond? Include the results (2)

Answer 6

(1) add a few drops of bromine solution, which is reddish-brown, to the alkene
(2) and the solution should decolourise, as the products are colourless

Question 7

TASK: draw the structure of sulfuric acid. (1)

Answer 7

mark your answer from the textbook p. 229

Question 8

TASK: draw the mechanism of the reaction between ethene & sulfuric acid to produce ethyl hydrogensulfate. (4)

Answer 8

mark your answer from the textbook p. 229

Question 9

When water is added to ethyl hydrogensulfate, ___(1)__ & sulfuric acid is formed. (1)
This means that sulfuric acid was a _____(2)____ in the reaction between ethene & __(3)__

Answer 9

(1) ethanol
(2) catalyst
(3) water

Question 10

When water reacts with ethene, ethanol is produced. What are the conditions needed for this reaction to occur? (3)

Answer 10

(1) steam
(2) a suitable temp. & pressure
(3) using an acid catalyst (e.g. phosphoric acid)

Question 11

TASK: draw the mechanism of the reaction between ethene & water to produce ethanol. (4)

Answer 11

mark your answer from the textbook p. 229