Volunteers needed
To help doing chemistry activities
(“Plant smells and molecules”)
with youngsters and their families
• Saturday, April17 (~ 10-2)
ACS Earth Day event, Martinez
• Sunday, April 18 (~ 9-1)
ACS at Boy Scout Jamboree, Pleasanton
Please email me if you can help.
Thank you!
Introduction to Unknowns
(You have about two weeks to complete each unknown)
For instructions and experimental details
see Chapter 10, pp.618 - …., in your Mayo text
For a list of Unknowns and their derivatives see our
ERES files
Sample “Unknown” problems are in our ERES Exam
Folder
Unknowns
Preliminary Tests pp. 618 - 626
1. What is typical of the molecules of compounds that
have an odor?
2. Which organic compounds tend to have a
"pleasant" odor? And which tend to have a "bad"
odor"?
3. What characteristic features do you find in the
molecule structure of organic compounds that have
a color?
Preliminary Tests
•
Mp. for solids
What needs to be remembered for a good mp. measurement?
Which compounds tend to have high mp.s? low mp.s?
•
Bp. for liquids
Which compounds tend to have high bp.s? low bp.s?
•
Refractive index for liquids a physical characteristic, defines a
compound
•
Ignition test information?
•
Test for unsaturation
•
Beilstein test for halogen (p.626)
Solubility Tests
(pp. 626 – 627)
What type of information do you get if your unknown
1. is soluble in water?
2. is soluble in NaOH and in NaHCO3?
3. is soluble in NaOH only, not in NaHCO3?
4. is soluble in dilute HCl solution?
5. is soluble only in conc H2SO4?
6. is not soluble in any of the above solvents?
After the Solubility tests you will do
Classification tests
(specific for a certain functional group)
Once you have a reasonably good idea what your
unknown could be (check ERES file),
you will prepare two
Derivatives
(related solid compounds with a defined, listed mp.)
Unknown #1
can be:
Aldehyde
Ketone
Alcohol
or Phenol
Aldehydes and Ketones
functional groups?
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
• Spectra
•Typical properties….
• Mp., bp., solubility…
Classification Tests for
Aldehydes and Ketones
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
2,4-dinitrophenylhydrazone
• Spectra
also a good derivative!
1. What are desirable properties of a derivative?
2. What is the purpose of preparing a derivative?
→Prepare two good derivatives of each unknown.
Recrystallize from ethanol/water.
Aldehydes and Ketones
• Preliminary tests
To distinguish between aldehydes and ketones:
• Classification tests
• Solubility
• Derivatives
• Spectra
• Tollens Test:
• Jones (chromic acid): check reagent! Test is also positive for …..?
• Schiff reagent: check reagent!
Always do with a known compound to compare!
Aldehydes and Ketones
Derivatives
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
Imines:
2,4-dinitrophenylhydrazone
oxime
semicarbazone
• Spectra
Alcohols and Phenols
Solubility distinction?
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
• Spectra
Solubility:
Alcohols: “neutral”;
Phenols: very weak acids, pKa around 10, except nitrophenols!
Classification tests:
• Jones (also positive with 1o, 2o alcohols, amines…!)
• Lucas test for 3o alcohols, 2o alcohols (slow):
• Phenols only: Complexation with Fe 3+
• Preliminary tests
Alcohol and Phenol Derivatives
• Solubility
• Classification tests
• Derivatives
• with 3,5-dinitrobenzoyl chloride
• Spectra
• urethanes
Similarly: Naphthyl urethanes
OCH 3
Anthocyanin Colors:
Phenolic plant pigments responsible for
blue, purple, pink colors in plants. HO
Can complex with metal ions in soil,
are pH sensitive
OH
+
O
OCH 3
O - glucose
OH
Cl
Malvidin
an anthocyanin in blue grapes
-
Aldehydes and Ketones
IR:
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
• Spectra
H-NMR:
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
• Spectra
IR:
H-NMR:
Exchange with
D2O
Alcohols
Phenols
Sample Compound: Phenol
IR
H-NMR
Next time (after Spring Break) :
Unknown 1 (cont.)
Unknown #2:
Carboxylic Acid, Ester, Amide, Amine
(Cl, Br, nitro)