The Cyclohexene + Bromine Water Prac? (1 Viewer)

[SuchSmallHands]

I'm having pretty major problems with the equation for the C6H10 + Br2(aq) (OR as I've seen elsewhere, OHBr OR HBrO + HBr) reaction. To clear this up I stupidly decided to check out the standards packages as this question thankfully came up in the 2002 HSC paper. So the first example (talking for bands 5/6 ofc) listed bromine water as Br2, which I'm not too keen on personally because it doesn't seem exactly accurate (it could be, if it is please explain if you can!) The second called cyclohexane C6H14, which is straight-out, unambiguously wrong. The third did the same, and labelled cyclohexene as C6H12 also. Finding what the products are is also difficult, is it just C6H10Br2 (1,2-dibromocyclohexane)?
Tl;dr, I'm absolutely lost on the first, and one of the easiest, pracs of HSC chemistry. Could someone give me a hand?

 

[tashe]

This question gets ask every year.

Maybe Someth1ng should make a detailed thread about the bromine water practical and sticky it.


Cyclohexene: C₆H_{10 (l)} + Br_{2 (aq)} -> C₆H₁₀Br_{2 (aq)}

Cyclohexane: C₆H_{12 (l)} + Br_{2 (aq)} -> N.R (No reaction) [obviously different when under sunlight]


1. The correct formula is Br_{2 (aq)}. The (aq) denotes the "water" in the word, "bromine water". To get technical ...http://community.boredofstudies.org...ohexene-bromine-water-234351.html#post4891519

2&3. Are you sure the examples are referring to cyclohexene and cyclohexane? They could be referring to hexene and hexane.

4. Yes, It is 1,2-dibromocyclohexane.

 

[SuchSmallHands]

This question gets ask every year.

Maybe Someth1ng should make a detailed thread about the bromine water practical and sticky it.


Cyclohexene: C₆H_{10 (l)} + Br_{2 (aq)} -> C₆H₁₀Br_{2 (aq)}

Cyclohexane: C₆H_{12 (l)} + Br_{2 (aq)} -> N.R (No reaction) [obviously different when under sunlight]


1. The correct formula is Br_{2 (aq)}. The (aq) denotes the "water" in the word, "bromine water". To get technical ...http://community.boredofstudies.org...ohexene-bromine-water-234351.html#post4891519

2&3. Are you sure the examples are referring to cyclohexene and cyclohexane? They could be referring to hexene and hexane.

4. Yes, It is 1,2-dibromocyclohexane.

Oops really? I didn't bother checking because I thought it was one of those really stupid things that I'm the first person to struggle with. If the Board is fine with Br2(aq) I'm not going to overcomplicate a very simple prac, but just out of curiosity, if you were to write bromine water like that in a condensed formula would it become C6H10 + HOBr + HBr --> C6H10Br2 + H2O?

Yes they were using cyclohexane/ene, all three specified cylco (http://arc.boardofstudies.nsw.edu.au/standards-packs/SP02_15050/) just seems so bizarre that the standards package would have two out of three of their top examples featuring obvious, easy mistakes; it's misleading. This is completely unrelated but tbh I hate the way the standards packages operate anyway, like an example of what a band 5/6 is is a massive range. Even just band 6 seems pretty ambiguous. It would be good if the actual mark was noted.

 

[QZP]

1. Most schools will do the bromine practical using cyclohexane/cyclohexene rather than hexane/1-hexene only due to hazardous reasons. It follows that you would use cyclohexane/cyclohexene for the first-hand investigation questions in exams. The alternative is acceptable; do what you are comfortable with (for me it is what was done in class).

2. Just specify bromine water as Br2(aq) --- this is the most common acceptable way. BrOH(aq) is also acceptable but it complicates your chemical equations so you shouldn't use this. For context (AFAIK), the HSC first used BrOH(aq) but then later also allowed Br2(aq) to avoid confusion. Again, do what you are comfortable with.

3. Cyclohexene (C6H10), Cyclohexane (C6H12) are correct.

4. The reactions are as follows (credits to tashe above; only using to make my post wholesome):
Cyclohexene: C6H10 (l) + Br2 (aq) -> C6H10Br2 (aq)
Cyclohexane: C6H12 (l) + Br2 (aq) -UV> C6H11Br (aq) + HBr (aq)

 

[skillstriker]

They accept both equations. I personally prefer the simple one (bromine water as Br2 (aq))

 

[SuchSmallHands]

I get that you could use hexane/ene, but all three specified cyclohexane/ene, then gave the formula for the regular molecule. Does it happen often in the standards packages that the top band examples have errors? Or are they generally trustworthy?

 

[SuchSmallHands]

They accept both equations. I personally prefer the simple one (bromine water as Br2 (aq))

Yeah, I think I'll go with that. No point making an easy practice difficult for no reason.