Organic Chem - Identifying Functional Groups

RolandIRL

Hi all,
i have to identify 5 samples (1,2,3 were solids, 4,5 were liquids) by classifying them as
1) Aliphatic or aromatic and
2) Carboxylic acid, amine (primary, secondary, tertiary) or ammonium carboxylate

We did a burn test on the solids, tested solubility in water (and test solution for pH), tested solubilty in HCl, and treatment with 10% NaOH, in that order

Results:
Burn Test: 1 - Clean flame, no smoke 2 - Yellow sparks, smoky-ish flame 3 - smoky flame
Solubilty in Water: 1 - Dissolved 2 - Dissolved 3 - Partially 4 - Partially in hot water 5 - Partially in hot water
pH: 1 - Acid 2 - Neutral (i think) 3 - Acid 4 - Basic 5 - Basic
Solubilty in HCl: 1 to 4 - Undissolved 5 - Dissolved
Addition of 10% NaOH: 1 to 3 - No smell but dissolved 4 and 5 both ahd a pungent smell
I had trouble smelling the samples as i have a cold

this is what i think they are:
1 is an aliphatic compound. 2,3 are aromatic.
Solution 1 is a simple carboxylic acid. Solution 2,3 are aromatic carboxylic acids.
Solution 4,5 are either amines or ammonium carboxylates. i can't figure out which.
Some results may be wrong (but hopefully they're not)
So can anyone clarify the functional groups?
Thanks

EDIT: Others in the lab did confirmatory tests (i didn't have time).
Test 1: Carboxylic Acid - Lime water test. (this involves boiling test tube of Na2CO3 to remove all CO2. then adding the sample, and connecting the test tube to a tube containg lime water. then boiling the lime sodium carbonate solution. when done, shake lime water and a white precipitate of CaCO3 is formed). they found 1 got a white precipitate. no other samples were done

Test 2: Amines - Nitrous Acid test:
solution A: dissolve 0.2mL of amine in 2-3mL of dilute HCl and cool the solution.
Solution B: cool solution of NaNO3

Mix the solutions.
In 4 a yellow oily colour was observed.
5 didn't show anything, so a cold solution of 2-naphthol in 10%NaOH was added to it. a red dye was observed.

from this i think 4 is a secondary aliphatic/aromatic amine and 5 is a primary aromatic amine. how to distinguish 4 from being aromatic or aliphatic?

The attachment is the procedure of confirmatory tests.

cianl1

You weren't given any spectroscopic data, by any chance, were you?

It just seems strange in this day and age to have to identify organic molecules by flame tests and pH and then guessing if it's a carboxylate or an amine.

What I would say is that you'd know aromatics and amines by odour.

Any more info you could offer would be good.

RolandIRL

it's first year labs so they don't let us anywhere near the expensive machines. we have to do it by basics.

for the 2nd test in the attached document, (the one with the FCl3), the solutions 1-3 were buff coloured, while solution 4 was green, and solution 5 was red.

pfishfood

Hi do you have a book called "Vogel's Quantitative Chemical Analysis" this should give you all the answers

RolandIRL

it's in the college library. i'll look it up tomorrow. will it help for all organic experiments?

craggles

Build an NMR, IR and Mass Spec :pac:

RolandIRL

Build an NMR, IR and Mass Spec

yeah, great idea, cos a 1st year student will really have the knowledge to do this :P

Capt'n Midnight

back in the day it was much easier , you just tasted them :P


[do not try this at home]:eek::eek::eek::eek::eek::eek::eek:

Kevster

Dude, this is simple if you're just willing to devote an hour of your time looking through books (or even online) about the properties of each class of compounds you're supposed to look up. Just look up general characteristics of the aliphatics and aromatics, firstly, and write them down. Then look up the characteristics of the carboxylics and amines.

...it's not that hard dude. You can't get hand-outs everywhere yuo go, and sooner or later you'll have to start doing the work ALL (yes...ALL) by yourself.

:P

RolandIRL

i've spent 2 evenings the college library looking up the net, and looking for books about functional groups, but they don't seem to give any characteristics of them and how to identify them in compounds. they all seem to give mechanisms of the groups
i think i was looking under the wrong titles - functional groups and the like.
the vogel book was a big help. thanks pfishfood

..it's not that hard dude. You can't get hand-outs everywhere yuo go, and sooner or later you'll have to start doing the work ALL (yes...ALL) by yourself.

all by myself??? :O

Kevster

GMIT...? **** library.