Soccerboi's questions thread

[soccerboi]

Personally I think having two Cs (or Hs or Os or whatever) next to each other not only looks silly but it can be awfully confusing, so avoid it wherever possible.

Yeh i was thinking it looked weird with the two Cs together, thanks a lot

[soccerboi]

Whats the strongest intermolecular force in CH4? Is it dispersion forces, or ionic( is this even present?)? How do u tell when ionic is present? Mann this is such a basic question, i should know it...

EDIT: I got it, its covalent bonds...

[charmanderp]

It's not covalent, as those aren't intermolecular forces. The strongest intermolecular forces are dispersion forces (in fact they're the only ones present).

Covalent bonds are intramolecular forces and again, they're the only ones present.

[soccerboi]

It's not covalent, as those aren't intermolecular forces.

Oh, ok so then its dispersion?

[pi]

It's not covalent, as those aren't intermolecular forces.

Oh, ok so then its dispersion?

Yes

[soccerboi]

Can someone explain how this is possible:

Each group took a 10ml aliquot of the 2M acid and diluted it to 250ml in a volumetric flask. The diluted acid solution was placed in a 50ml burette.

When i read it just doesnt sound possible. Hows 250ml fit into a 50 ml burette? I must be interpreting it wrong somehow?

[vgardiy]

They just mean some of the solution was put in it.

[soccerboi]

oh ok, the mol would be changed but the concentration of the solution would be the same right?

[vgardiy]

Assuming you washed it with the solution from the volumetric flask, the concentration would remain constant.

[soccerboi]

thanks 

[Mao]

In mass spec equations, how do we know where to put the charge? Is it just where fragment comes off, or always at the end of the formula?
Like the one below, if the CH3O comes off, how do u write the fragment that will show the peak on the spectrum? CH3COOCO⁺?

Also how do u write the semistructural formula for it? CHCOOCOOCH3 or CHOOCCOOCH3?

I would say CH3OOCCOOCH3. This structure implies the carboxyl oxygens are to the left of the bolded carbon. And likewise for the other carbon in the centre

If you were to write CH3COOCOOCH3 would imply the carboxyl oxygens are to the right, which is false.

If you were to write CH3OCOCOOCH3 or any other combination with CH3O(C2O2)OCH3, that will be fine. Though far more commonly, it will be written as Me₂Ox, where Me=methyl and Ox=oxalate.

[soccerboi]

In mass spec equations, how do we know where to put the charge? Is it just where fragment comes off, or always at the end of the formula?
Like the one below, if the CH3O comes off, how do u write the fragment that will show the peak on the spectrum? CH3COOCO⁺?

Also how do u write the semistructural formula for it? CHCOOCOOCH3 or CHOOCCOOCH3?

I would say CH3OOCCOOCH3. This structure implies the carboxyl oxygens are to the left of the bolded carbon. And likewise for the other carbon in the centre

If you were to write CH3COOCOOCH3 would imply the carboxyl oxygens are to the right, which is false.

If you were to write CH3OCOCOOCH3 or any other combination with CH3O(C2O2)OCH3, that will be fine. Though far more commonly, it will be written as Me₂Ox, where Me=methyl and Ox=oxalate.

Thanks Mao, so when writing semi structural formulas, it's safest to just write the elements out in order of appearance?

[ggxoxo]

I was just wondering why hydrolysis for peptide and glycosidic links require concentrated acids. Shouldn't we have dilute to provide H2O for hydrolysis?

[soccerboi]

Unsaturated fats are reacted with hydrogen gas using a metal catalyst to produce saturated fats. To produce a
saturated fat, 7.50 g of hydrogen gas was reacted with 1.25 mol of unsaturated fat.
Assuming the unsaturated fat is a triglyceride containing only one type of fatty acid, which of the following
fatty acids was the constituent of the unsaturated fat?
A. linoleic acid
B. arachidonic acid
C. linolenic acid
D. palmitoleic acid

[Reckoner]

Unsaturated fats are reacted with hydrogen gas using a metal catalyst to produce saturated fats. To produce a
saturated fat, 7.50 g of hydrogen gas was reacted with 1.25 mol of unsaturated fat.
Assuming the unsaturated fat is a triglyceride containing only one type of fatty acid, which of the following
fatty acids was the constituent of the unsaturated fat?
A. linoleic acid
B. arachidonic acid
C. linolenic acid
D. palmitoleic acid

Firstly, we need to recognise that one H₂ so the molecule will be placed across one c=c, finding the mole ratios will help with the question.

There are 3.75 moles of H₂ to 1.25 moles of the fat, so the 3:1 ratio of H₂:fat indicates that there are 3 c=c bonds in the fat.

As it is a triglyceride, there are 3 fatty acids, and as all of the three fatty acids are the same, the fatty acid must contain 1 c=c bond each. Therefore, the answer is D, palmitoleic acid.

I hope this is correct...