Question

http://maxpapers.com/wp-content/uploads/2012/11/9701_w14_qp_12.pdf
q30

Answer 1

Is the answerC?

Answer 2

that's what i have thought at the beginning but it turned out to be B

Answer 3

Ok, let me see it. That's the exam paper I did last year though...

Answer 4

oh take your time, so how was your grade?

Answer 5

Was an A.

Answer 6

congrats on that (Y). Have you got any practical notes?

Answer 7

You mean for paper 3?

Answer 8

Thanks.

Answer 9

yes, your welcome.

Answer 10

Practically not. We just made notes on how to make tables very accurately.

Answer 11

i am retaking AS level chemistry on this june . I scored a U im my practicals but scored two A's in my other two papers and i will be doing A2(not a retake) next to it too.

Answer 12

I think I got it why is it B now.
You should know that when unsaturated parts react with hot KMnO4, this first breaks the double bond into a diol and the OH parts eventual turn into a carboxylic acid group or ketone groups. As for all unsaturated parts out of the two enclosed structures, the double bonds after breaking will have two free more bonds to make, hence they can be carboxylic acid. As for the ones inside the enclosed part, they only have 1, because the 2 other parts are already bonded to the carbon, so it will make a double bond with an oxygen, making a ketone. Each unsaturated part inside the enclosed structure can make 3 different ketones, giving a total f 6.

Answer 13

Good luck then. So you will be doing papers 3, 2 and 5 right?

Answer 14

no, i have to repeat all papers :( . in addition to paper 4 and paper 5. well, if it has one hydrogen bonded to a carbon atom, the molecule would be oxidized into an alcohol and eventually further oxidises into a carboxylic acid.

Answer 15

Correct.

Answer 16

Red arrows is where i think ketones would be produced, only C atoms attatched to CH3 and to the rest of the chain.

Answer 17

not the other carbon atom bonded to a hydrogen atom

Answer 18

Within your red arrows, only the ones pointing at the double bond inside the enclosed structured will turn into a ketone, because they have 2 fixed bonds already to the Carbon and thus if it oxidises, it can convert the other 2 into a ketone, whereas for the others, the Carbon will be having only 1 fixed bond and with the 3 free, it makes a carboxylic acid.

Answer 19

The starting C=C and the ending C=C do turn into a ketone, yes?

Answer 20

Yes and each of them makes 3 different ketones.

Answer 21

shouldnt it be 4 ketones

Answer 22

No. In each of them, the part of the double bond attached directly to CH3 can only make one, whereas the other end can make 2.

Answer 23

i am talking about the double bond at each end of the structure, yes they will produce 2 different ketones, and the C=C bonded to CH3 will only be oxidised to a ketone the other
C atom wont.

Answer 24

Yes.

Answer 25

How is that a 6 molecule then.

Answer 26

Let me recap. The correct arrows are the ones pointing at the double bonds inside the enclosed structures and each one of them makes 3 different ketones, making a total of 6 .

Answer 27

okay, three different ketons are the C=C at the end the 3rd C=C and the 3rd is?

Answer 28

O. They are in your first and last showed arrows.

Answer 29

The C=C at each end are the same its just rotated, they should be the same i think.

Answer 30

Yes, they are.

Answer 31

they should produce the same ketons then.

Answer 32

Yes.

Answer 33

2nd and 5th arrow are also the same right they would produce the same ketone but here only one carbon atom is oxidised.

Answer 34

same goes to the 3rd and 4th arrow right?

Answer 35

Yes, but those ones would form carboxylic acid instead of ketones, as I said before.

Answer 36

i am not saying that two C atoms involved in double bonding will form a ketone but only the carbon atom attatched to CH3 will form a ketone. we should take this into account.

Answer 37

Oh, yes. You got it.

Answer 38

i counted the one carbon atom being oxidised as whole different molecule. Thanks for your help and time :)

Answer 39

No problem. Hope you do well this June. I will keep on praying for you.

Answer 40

Thanks, same here :)