Unit 3 Questions MEGATHREAD :)

[pi]

WHAT DO I  NEED TO KNOW FOR ASPIRIN??
holy crap, im gonna cram for aspirin 6 hours after accounting exam tmrw..

You don't need to any specifics actually. It only might be helpful to know what happens, but it isn't essential knowledge

[nacho]

Beta-d-glucose and Galactose differ at carbon 4; in galactose the OH sticks up, in glucose the OH sticks down.

wait i thought it was:

a-glucose, OH sticks down
B-glucose, OH sticks up


and what about alpha-glucose, how does that differ from galactose, if my thoughts are incorrect

[azure]

Hello I need a little help with this question please, very unsure even though I've read the solutions.
2011 Insight, Q6b
I was wondering about the carboxylic func. group on the other end of alanine... would that make it acidic in water as well?

[cltf]

Hello I need a little help with this question please, very unsure even though I've read the solutions.
2011 Insight, Q6b
I was wondering about the carboxylic func. group on the other end of alanine... would that make it acidic in water as well?

It would be basic because the dipeptide has more NH2 functional groups than COOH. If you imagine sticking the dipeptide in water, the COOH will DONATE, whilst the NH2 will ACCEPT, but overall more is accepted than is donated. Thus if it accepts more it is more basic.

[azure]

Hello I need a little help with this question please, very unsure even though I've read the solutions.
2011 Insight, Q6b
I was wondering about the carboxylic func. group on the other end of alanine... would that make it acidic in water as well?

It would be basic because the dipeptide has more NH2 functional groups than COOH. If you imagine sticking the dipeptide in water, the COOH will DONATE, whilst the NH2 will ACCEPT, but overall more is accepted than is donated. Thus if it accepts more it is more basic.

Ohhhhh so taking into account of the NH2 in the side chains as well? Thank you! Understand now

[luken93]

Beta-d-glucose and Galactose differ at carbon 4; in galactose the OH sticks up, in glucose the OH sticks down.

wait i thought it was:

a-glucose, OH sticks down
B-glucose, OH sticks up


and what about alpha-glucose, how does that differ from galactose, if my thoughts are incorrect

the very left carbon, glucose sticks down, galactose sticks up - this is 4-C

The difference between a and b glucose is the very RIGHT carbon atom, a-glucose OH sticks down, b-glucose OH sticks up - this is 1-C

[nacho]

fair enough, but thinking about it in a 3-d manner.

wouldnt that mean that a glucose is the same as glucose and b glucose is the same galactose?
Or am i just unable to comprehend the logic behind this..lol
sigh C+ for chem, why not

[homosapiens]

1. What kinds of reactions does benzene undergo? I would have thought combustion and addition (because of the double bonds) but apparently it's substitution, not addition? Is this because the shape must be maintained?

2. When say ethane reacts with chlorine when there's UV light, is CH3CH2Cl the only possibility, ie can CH2ClCH2Cl also be formed? And if so is it just that chloropropane is more likely than 1,2-dichloropropane...

1. [OUT OF COURSE] Benzene undergoes substitution because the fact that it's aromatic makes it highly stable; if you try to add to benzene you have to break this stability, this aromaticity, and that's unfavourable. Benzene instead undergoes substitution, that's correct. You don't need to know this though - I think all you need to know is that benzene does not act like a normal alkene.

2. Yes, you can get two chlorines thrown in. In fact, you can get as many chlorines thrown in as you want; it depends on the relative proportions of chlorine and ethane - whether chlorine is in excess or not.

Thanks thushan! Stumbled across the benzene one in a Neap topic test so I thought it'd be best to double check (:

[homosapiens]

Trying to categorise molecules into HPLC and GC: I know carbohydrates can't be vaporised, what about nucleic acids, lipids and proteins?

[mickeymouse]

just wanting some clarification: in fractional distillation involving a tower and crude oil those with a higher molecular mass are collected at the bottom (higher temperature) but fractional distillation in general would result in those with a lower molecular mass collected first and so they are at the bottom?

[mickeymouse]

Trying to categorise molecules into HPLC and GC: I know carbohydrates can't be vaporised, what about nucleic acids, lipids and proteins?

apparently proteins decompose upon heating so I don't think they will vaporize either

[Andiio]

Why are the chem shift values for 13C huge in comparison with that of 1H?

[homosapiens]

just wanting some clarification: in fractional distillation involving a tower and crude oil those with a higher molecular mass are collected at the bottom (higher temperature) but fractional distillation in general would result in those with a lower molecular mass collected first and so they are at the bottom?

Not sure if this answers your question, but the temperature decreases up the column, and fractions with lower boiling points liquefy out first because the temperature drops below their boiling temperature first

[homosapiens]

Trying to categorise molecules into HPLC and GC: I know carbohydrates can't be vaporised, what about nucleic acids, lipids and proteins?

apparently proteins decompose upon heating so I don't think they will vaporize either

ok so just to confirm... carbohydrates and amino acids need to go through HPLC and lipids and nucleic acids can go through GC

[lilaznkev1n]

really noob question but can you please explain the secondary structure of proteins. I know it is due to hydrogen bonds which will cause coiling and folding but I don't know much else.
My book says hydrogen bonds form between C=O and H-N, I don't really get this because isn't this a peptide link which is a covalent bond?