Error on Form AM PS section

[myst]

Anyone notice this? There was a question regarding energy i think and the persons weight was 76g (not kg).. none of the answers worked if 76g was used in the calculation

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[myst]

Anyone notice this? There was a question regarding energy/work (the skiing question) i think and the persons weight was 76g (not kg).. none of the answers worked if 76g was used in the calculation

am i the only one that saw this?

 

[Mutt]

They were Lilliputians.

 

[Mutt]

By the way, can a D-pentose be levorotatory?

 

[Jon Davis]

You'd have to do an experiment for that since it has many chiral centers. In the straight chain form I suspect it is dextrarotary (sp?).

 

[Mutt]

that's what I thought, but on one of my BS sections it said "D-allose, a levorotatory sugar..." and it caught my eye because if it were levorotatory, I thought it would be L-allose....can anyone make sense of this?

 

[dsh]

I didn't have this form (CK), but on one of my problems it somehow involved finding the energy of a photon using e = hv = hc/lambda. the wavelength was given in nm but in every single answer choice it was put in as 10^-7.

 

[medstu2006]

that's what I thought, but on one of my BS sections it said "D-allose, a levorotatory sugar..." and it caught my eye because if it were levorotatory, I thought it would be L-allose....can anyone make sense of this?

D-Allose and L-Allose, although they mean dextrarotatory and levorotatory, tell us whether the OH group is on the right side or the left side of the last chiral carbon. When it says that it's a levorotatory sugar, it means that D-allose rotates light to the left. Rotation of light has nothing to do with a sugar being D-sugar or L-sugar and rotation has to be determined experimentally.
I still think that they could have made the sentence less confusing.

 

[Mutt]

D-Allose and L-Allose, although they mean dextrarotatory and levorotatory....

This is exactly my point. If it says "D-", then it should be a dextrorotatory sugar, right?

I understand the issue of optical rotation with regard to (+) and (-), but this is really screwey....

 

[jessdog]

This is exactly my point. If it says "D-", then it should be a dextrorotatory sugar, right?

I understand the issue of optical rotation with regard to (+) and (-), but this is really screwey....

I'm pretty sure D- and d- are different. small d is dextrototoatory and Big D has to do with what side the -OH group is on.

Jess

 

[blowe46]

I'm pretty sure D- and d- are different. small d is dextrototoatory and Big D has to do with what side the -OH group is on.

Jess

this was on the AM bio section?

 

[Machination]

I thought that question was alpha and beta anomers; a stand alone right?

this was on the AM bio section?

 

[blowe46]

I thought that question was alpha and beta anomers; a stand alone right?

i honestly don't remember but i don't recall it being on my test. I had form AM. i hope i didn't skip it. anyway, i can't beleive people still care about this... let it go.
worst case scenerio you write it again.

It's all out of our HANDS.

 

[stoleyerscrubz]

When sugars are named with "D" the last(bottom) OH group is on the right side of a fisher projection and on the left side when you see "L". You can not predict the specific rotation d/+ or l/- from this. but you would be able to determine if it is R/S configuration.

I'm pretty sure D- and d- are different. small d is dextrototoatory and Big D has to do with what side the -OH group is on.

Jess