Exam Suggested Solutions

[Mao]

i thought it's just minimising numbers?

where art thou, coblin~


as for that H+ thing, revert that, Coblin has a better explanation that is against it

however, VCAA will most likely accept H+ as an answer

[equinox]

Question 6
a
    i (2 marks)
    ethylamine

    ii (2 marks)
    5-chloro,2-methylheptane


is 2,methyl 5,chloroheptane ok

[annie]

Question 6
a
    i (2 marks)
    ethylamine

    ii (2 marks)
    5-chloro,2-methylheptane


is 2,methyl 5,chloroheptane ok

Mao can you upload the image of the structural formula =D
please??

[Collin Li]

mao: shutup that doesn't even EXIST lol. it's impossible! coblin reminded me.

I lost 1 mark.  Wrote H+ for fragment instead of H (i'm a retard like that).

Isnt H+ correct as the H's get bombarded with electrons which knock electrons out of the shells of the atoms.
Hmmm

technically, yes, as both fragments would've lost electrons.

, where that electron will go with the flow and run off somewhere else

That's wrong. Fragmentation does not gain or lose electrons. Fragmentation is a process that occurs because of the ionisation process (and is not an ionisation process itself), because the molecule that bears a positive charge is unstable.

For a fragment of 45 m/e to occur, the CH3CH2O must be positively charged (simply to be detected), while the neutral H atom leaves with an electron. For the purposes of mass spectrometry, we typically assume that there is only an overall positive charge of 1, as ionisation of 2 electrons is rare.

[equinox]

Hey Mao what was the exact wording of the question?  This might help sort out this debate.

[jfaure]

ethylamine and aminoethane are the same thing, yer??

[nathankb]

i agree 100% with coblin...i wrote CH3CH2O+...this is the fragment which provides a 45 m/z ratio

[equinox]

it asked for what was the OTHER fragment i think.

[Mao]

i agree 100% with coblin...i wrote CH3CH2O+...this is the fragment which provides a 45 m/z ratio

no, the question asks

What fragment must have been lost from the molecular ion to account for the high peak at m/z 45?

hence, the answer is H

[ps, the exact wording of the question was already in the first post ]

[Collin Li]

ethylamine and aminoethane are the same thing, yer??

Yep. In an earlier post:

Pahahha I wrote ethamine.

This is wrong.

Ethanamine, ethylamine or aminoethane are acceptable.

This site shows all the synonyms of this molecule: http://www.chemindustry.com/chemicals/651358.html

The way I remember whether it is ethanamine or ethamine is because the "an" in ethanamine indicates that it is saturated. If I was talking about ethenamine, how could I represent that in the shorter name? Ethemine? Hehe.

[Mao]

Question 6
a
    i (2 marks)
    ethylamine

    ii (2 marks)
    5-chloro,2-methylheptane


is 2,methyl 5,chloroheptane ok

Mao can you upload the image of the structural formula =D
please??

its up.

equinox: no, that will be wrong.

5-chloro,2-methylheptane
 is the correct one

2-methyl,5-chloroheptane
 is also accepted, but not correct according to IUPAC

[annie]

VCE Chemistry Unit 3 Exam


the graph:

    ii (2 marks)
   

Code: [Select]

    Cl    c
    |     |
c-c-c-c-c-c
          |
          c
    5-chloro,2-methylheptane

damn, i got 6 - methyl , 3 - chloroheptane for this one

Somehow it looked liek the 3rd carbon to me....

[Collin Li]

Question 6
a
    i (2 marks)
    ethylamine

    ii (2 marks)
    5-chloro,2-methylheptane


is 2,methyl 5,chloroheptane ok

Mao can you upload the image of the structural formula =D
please??

its up.

equinox: no, that will be wrong.

5-chloro,2-methylheptane
 is the correct one

2-methyl,5-chloroheptane
 is also accepted, but not correct according to IUPAC

Those commas should be dashes.

[ben4386]

i agree, i always thought u start naming from the end closest to any functional group?

edit : according to the nelson book the carbons in the main chain are numbered from the end nearest the first chlorine

[annie]

i agree, i always thought u start naming from the end closest to any functional group?

edit : according to the nelson book the carbons in the main chain are numbered from the end nearest the first chlorine

page reference?