Question

Urgent HELP with chem Lab problem!!! please! medal and fan

Answer 1

The functional groups present on the outside of large molecules can help to determine the solubility of a molecule. The compounds A and B have been dissolved in a solvent.

1). Dr. Bunsen Honeydew wishes to separate the compounds by the addition of another solvent (as we did in the milk lab). Dr. Honeydew performed his separation based largely on changes in polarity, so he added methanol to the mixture. Upon addition of the methanol, one of the two compounds precipitated.
a. Describe the properties of the original solvent and methanol, and justify why the methanol would be a good solvent to choose for this separation. (2 pts)
b. Predict which compound was precipitated. Justify your choice by describing the types of intermolecular forces present in the compound and the solvents (polar, non-polar, etc.).


2). Another way to separate compounds is to prepare a salt by the addition of HCl (see the label on many medicine containers: i.e., Benadryl is diphenhydramine hydrochloride.)
a. Suppose you have compounds A and C, which compound is more likely to form a hydrochloride salt?
b. The reaction that forms the salt is an example of an acid-base reaction. If HCl is the acid, what groups on the compound that forms a salt are behaving as a “base”?
c. Once the salt is formed, describe the solvent system (a solvent that would dissolve both compounds and a second solvent that would selectively precipitate one of the compounds) that would separate the salt from the mixture

Answer 2

@aaronq last one. after that u will never hear from me again lol

Answer 3

hmm can't see the pictures :S

Answer 4

do you think you can rate them in order of polarity?

also, which one (is not like the others) and will precipitate in methanol?

Answer 5

no, how do you know which is more and which is less polar?

Answer 6

it's based on the functional groups.

which one is more polar?

Answer 7

here this might help:

http://organicchemistryorganicchemistry.blogspot.com/2008/04/functional-group-polarity.html

Answer 8

So the one with OH is more polar?

Answer 9

and so C precipitates in methanol?

Answer 10

@aaronq ??? i need to turn this in asap please help me!

Answer 11

@ganeshie8 can u help me please?

Answer 12

most polar A > B > C

A would precipitate in methanol

Answer 13

C is not even a candidate for precipitation

"The compounds A and B have been dissolved in a solvent...Upon addition of the methanol, one of the two compounds precipitated. "

Answer 14

ooh wow! yea this is where i start to freak out before its due

Answer 15

@aaronq this is what i put for A: Methanol is a simple alcohol and it doesn't interfere with the reaction but allows compounds to exist in ionic forms like water would normally

Answer 16

so what about the second part. and then i will be done with this report!!

Answer 17

@aaronq please help me i only got 1 hour left!!!

Answer 18

for A i put A the one with the OH, for B i put the hydroxide group

Answer 19

Non-polar compounds can't be salts, so it would be A (if you deprotonate the OH's you're left with alkoxide ions and \(Cl^-\) is the counter ion when they salt out of solution

Answer 20

yep thats right

Answer 21

so what would be the solvent system for C

Answer 22

to extract the salt out of the mixture you would use a very polar solvent. Then once you isolate it, you use acid to reprotonate the OH's.

Answer 23

so would this polar solvent be methanol?

Answer 24

no i would use something like chloroform, or tetrahydrofuran

Answer 25

ok cuz in the question they are asking for 2 different solvents

Answer 26

okay so the first is polar, then the protonated form will precipitate in alcohol, propanol is fine

Answer 27

ok thank you so much!! i wish i could thank you in any other way!!

Answer 28

no problem dude! sorry it took me awhile, I'm doing homework too

Answer 29

thats absolutely fine as long as i get it turned in time!

Answer 30

good stuff