Chemistry 3/4 2013 Thread

[Alwin]

Hey guys!

So my result compared to my teachers result was 0.01% off. (Her's was 0.3% compared 0.29% which was mine) What error could have possibly happened?

A lot haha. Write out the question and see what we come up with. Otherwise, check your use of significant figures and any rounding of your numbers (both working and solution) compared to your teacher's numbers.

[Homer]

Hey guys, im having trouble understanding NMR! the book talks about the radio waves causing a change in overall spin of the atom, but im still alil confused :/

[thushan]

http://www.chemguide.co.uk/analysis/nmrmenu.html

MY BIBLE.

[Sapphire]

Just clarifying something;
I read that functional groups of Hydrogen do not cause any splitting of the NMR signal of their neighboring protons. Is this true? Can someone show me an example

[jgoudie]

I think what you mean are things like alcohols (OH) carboxyl (COOH) and Amine (NH₂).  With these functional groups the Hydrogen is on the other side of the oxygen/nitrogen, thus we get singlets.

eg.  CH₃CH₂OH

The H in hydroxyl is shielded by the oxygen and forms a singlet.
The H₂ will form only a quartette due to the H₃ on the left, the OH does not interfere with the signal.
The H₃ will form a triplette due to the H₂ to its right.

Hope this makes sense. There are also few videos on spectroscopy and such in my youtube channel, you can see the link below.

Just clarifying something;
I read that functional groups of Hydrogen do not cause any splitting of the NMR signal of their neighboring protons. Is this true? Can someone show me an example

[Limista]

^ jgoudie, are you in year 12? Asking out of interest 

[jgoudie]

No, I am a Year 12 teacher.

^ jgoudie, are you in year 12? Asking out of interest 

[Stick]

What takes precedence when numbering (and hence naming) hydrocarbons - the double bond or the functional group?

[Edward21]

Question, with balancing a combustion reaction, is it ok to have a fractional coefficient? I've seen it before, but my teacher says I shouldn't do it because it may be VCAA marked down? Any thoughts/contributions to this?

[Daenerys Targaryen]

I've done it with fractions too, but I've noticed my teacher not using fractions; mind you I've never questioned it before. In saying that, I have kind of changed to doing with whole numbers - not that much harder to do just times by the denominator

[Sapphire]

I think what you mean are things like alcohols (OH) carboxyl (COOH) and Amine (NH₂).  With these functional groups the Hydrogen is on the other side of the oxygen/nitrogen, thus we get singlets.

eg.  CH₃CH₂OH

The H in hydroxyl is shielded by the oxygen and forms a singlet.
The H₂ will form only a quartette due to the H₃ on the left, the OH does not interfere with the signal.
The H₃ will form a triplette due to the H₂ to its right.

Hope this makes sense. There are also few videos on spectroscopy and such in my youtube channel, you can see the link below.

ah, I get it now thanks a lot for that!

[brightsky]

What takes precedence when numbering (and hence naming) hydrocarbons - the double bond or the functional group?

functional group...not including halogen substituents.

[09Ti08]

Hello,

Does anyone know what 1-butyl ethanoate is? This chemical is mentioned on question 16 (page 159-Heinemann) and I'm not sure what it is. I gave it a search but all the information came up was about butyl acetate?!

Thank you!

[Alwin]

Hello,

Does anyone know what 1-butyl ethanoate is? This chemical is mentioned on question 16 (page 159-Heinemann) and I'm not sure what it is. I gave it a search but all the information came up was about butyl acetate?!

Thank you!

1-butyl ethanoate is an ester. If you haven't hit organic chemistry, you will soon and learn all the fun things about esters! Its just butane and ethane "joined" together by an ester bond. not very technical, but gives you a rough idea. If you do read ahead/when you learn about esters then you will realize it is actually ethanoic acid and 1-butanol condensation/esterfication equillibrium reaction that results in 1-butyl ethanoate. I'm trying not to give away all the surprises and enjoyment of esters that your teacher undoubtably has in store for you

[brightsky]

it's an ester. and acetate = ethanoate. acetate is the older name; ethanoate is the iupac-endorsed name.

EDIT: beaten