Chemistry 3/4 2013 Thread

[lzxnl]

There IS only one functional group, so there are no alphabetical concerns here.

[hardworker]

Just wondering if anyone could help me with these organic chem questions.

out of these 3 which are isomers of butanol? 

CH3CH2CH(OH)CH3
(CH3)3COH
CH3COCH2CH3 

Which of the following has the highest boiling point
1-butene
1-butanol
butane
1-chloro propane

which of the following pairs of compound can be used to prepare CH3OOCCH3

Ethanol and methanoic acid

or

Methanol and methanoic acid

or

or methanol and ethanoic acid   

Which of the following Hydrocarbins can be formed by dehydration of 2 butanol

butene

or

butane

or

2 methylpropene

or

2 methyl propane

 

[hardworker]

 And what equation involves the equation for the conversions of propane to ethene.

Thanks in advance

[Homer]

I want to know the answers to these too!

My guesses:

1)CH3CH2CH(OH)CH3
2)1-butanol
3)methanol and ethanoic acid   
4)butene

[Daenerys Targaryen]

1. CH3CH2CH(OH)CH3
(CH3)3COH
They seem both correct to me

2. 1-butanol - H bonding

3. methanol and ethanoic acid   

4. butane

[Daniel_Le]

Hello,

I'm just have a question on naming with amines, would be 2-Aminohexane or 2-Hexylamine? I see in some places they use the prefix amino whereas in some other text they use amine, is either accepted to use?

Thank u

[thushan]

hexan-2-amine

2-hexylamine and 2-hexanamine are both acceptable, but technically not the IUPAC name. 2-aminohexane is wrong under the new nomenclature, since the amino group is a principal functional group and should go at the end as -amine instead of amino-

[Daniel_Le]

hexan-2-amine

2-hexylamine and 2-hexanamine are both acceptable, but technically not the IUPAC name. 2-aminohexane is wrong under the new nomenclature, since the amino group is a principal functional group and should go at the end as -amine instead of amino-

For this particularly molecule, I would like to ask what would be the name?

Spoiler

2-pentylamine or pentan-2-amine (2-pentanamine)? I found this particularly confusing because does not 'yl' signify branch? Generally we may have something like 4-methylbutane, which means there is a methyl substituent  located on the 4th locant of butane molecule and that butane molecule is itself the main carbon chain. But in this case, 2-pentylamine, does that mean amine is acting like the main carbon chain and we have a substituent of a pentyl on the 2nd locant? (Or maybe it is the naming in a reverse way? Like, it means the amine group is on the 2nd locant of the pentyl molecule?) I'm think I'm just not sure on how they came up with these 2 ways of naming it? (2-pentylamine and pentan-2-amine/2-pentanamine)? If someone can explaining to me would be very much great.

You would also thinking that VCAA would not put something like 2-aminopentane (old) in the exam due to the state of the new nomenclature? Or student would expected to know that molecule is the same as the above, etc?

Thank you,

[FlorianK]

For electrolosis, how do I know which ions in the solution are being electrolysed and what the required voltage is?

Let's say you have a 1-molar NaCl solution with graphite electrodes.

Possibilities at the Cathode with potentials including overpotentials :
Na⁺ + e^- --> Na E=-2,71V
2 H₃O⁺ + 2e^- --> H₂ + H₂O E=-1,41V

Possibilities at the Anode with potentials including overpotentials:
2Cl^- --> Cl₂ + 2e^- E=+1,66V
4OH^- --> O₂ + 2H₂O + 4e^- E=1,92V

Here we would produce Hydrogen and Chlorine with a required voltage of 1,66V - (-1,41V) = 3,07V. This would suggest to me that the Cation with highest electrode potential and the Anion with the lowest electrode potential would be electrolysed.

But what if we would have a 1-molar solution of SilverIodid and graphite electrodes?
Because suddenly the electrode potential of the Cation (Silver) is higher than that of the Anion (Iodid)?
Would the reaction thrive itself? Because 0,54V-0,8V= -0,26V?

[09Ti08]

Hello, in reaction pathways, do you think that it is a must to include the states of reactants and products? If yes, can you please point out specifically which one that is? I'm confused, my teacher said that I did not need to memorize all the states, but when I tried past exam papers, I think the assessors expect me to know about this... Thank you very much!

[aestheticatar]

Sup guys,
Sorry to ruin the trend in posting questions about organic molecules but I have a question regarding TLC. When and why should ethanol (or another solution) be used as the mobile phase instead of water?

Thanks heaps in advance

[Limista]

Sup guys,
Sorry to ruin the trend in posting questions about organic molecules but I have a question regarding TLC. When and why should ethanol (or another solution) be used as the mobile phase instead of water?

Thanks heaps in advance

Ethanol is non-polar, whereas water is polar.

Ethanol should be used as the mobile phase if the solute is also non-polar, because this means that the solute will be able to adsorb onto the stationary phase and desorb. This adsorption can only occur if the solute is able to be dissolved in the mobile phase.

This is because of the like-dissolves-like principle. Non-polar solutes will dissolve more easily in non-polar solvents.

[brightsky]

Ethanol is non-polar, whereas water is polar.

Ethanol should be used as the mobile phase if the solute is also non-polar, because this means that the solute will be able to adsorb onto the stationary phase and desorb. This adsorption can only occur if the solute is able to be dissolved in the mobile phase.

This is because of the like-dissolves-like principle. Non-polar solutes will dissolve more easily in non-polar solvents.

ethanol is polar too. :p

the only reason i can think of is because ethanol is pure while water can have random ions dissolved in it.

[Limista]

ethanol is polar too. :p

the only reason i can think of is because ethanol is pure while water can have random ions dissolved in it.

Yeah ethanol is polar because of the hydroxyl functional group. But it is also non-polar. It serves a dual purpose.

Water is only polar. So in water you can only dissolve polar solutes. In ethanol, you can dissolve both.

Therefore, in the context of this question: when should ethanol be used instead of water? If the solute is non-polar.

And ethanol is not necessarily pure, for the same reasons as water. Yeah, it's pretty vague 

[Mr Keshy]

Edit: I don't feel it's accurate so I'd rather not misinform. Haha