Today:Today:
Unknown 1 (review)aldehyde, ketone, alcohol, phenol
Unknown #2:
carboxylic acid, ester, anhydride, amide, amine(Cl, Br, nitro)
Questions?Questions?
2,4-dinitrophenylhydrazone (2,4-DNP)
Classification Tests for Aldehydes and Ketones
also a good derivative! →Prepare two good derivatives of each unknown if possible.
Recrystallize from ethanol/water.
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
• 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
To distinguish between aldehydes and ketones:
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
Aldehydes and Ketones Derivatives
Imines:2,4-dinitrophenylhydrazone
oximesemicarbazone
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
Alcohols and Phenols
Solubility distinction!
Solubility:
Alcohols: “neutral”;
Phenols: very weak acids, pKa around 10, except nitrophenols!
Classification tests:
• Jones (positive for 1o, 2o alcohols, aldehydes, amines…!)
• Lucas test for 3o alcohols, 2o alcohols (slow):
• Phenols only: Complexation with Fe 3+
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
• Spectra
Alcohol and Phenol Derivatives
• with 3,5-dinitrobenzoyl chloride
• urethanes
Similarly: Naphthyl urethanes
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
• Spectra
• the ratio of the velocity of light in air to the velocity of light in a given medium.
• sin incident angle/sin refracted angle
• a constant at a given temperature.
• an important physical property of liquids (and gases and transparent solids!)
• Air has a refractive index of 1.000292 at 273 K/760 mm Hg for the yellow sodium D-line at 589.3 nm.
Refractive IndexRefractive Index (confirming liquid unknowns)
Preliminary test results?
Mp., bp. Which would you expect to have relatively high/relatively low mp.s / bp.s?
Odor Which would you expect to have a bad smell/a pleasant smell (human perspective…)
Color Which would you expect to have a color?
• Preliminary tests?
• Solubility
• Classification tests
• Derivatives
• Spectra
Carboxylic Acids Anhydrides Esters Amides Amines Nitro
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?
Solubility Tests
Carboxylic Acids Anhydrides Esters Amides Amines Nitro
• Preliminary tests
• Solubility?
• Classification tests
• Derivatives
• Spectra
Carboxylic AcidsGood mp.s (consider recrystallization)
Neutralization Equivalent (titration) experimental instructions on our webpage
• Solubility
• Classification tests
• Derivatives (not done)
• Spectra
Derivatives (we do not do them in the lab):
Convert carboxylic acid into acid chloride first, then into amides
RCO2H + NaOH RCO2(–) Na(+)
aq. + H2O
1.
2.
+ HCl
Define carboxylic acid by: mp., neutr. equivalent, an ester and its bp.
Esters
Classification Test
Deep-red to purple
• Preliminary tests?
• Solubility
• Classification tests
• Derivatives
• Spectra
Compare with known ester!
a hydroxamic acid
Derivatives for Esters
Hydrolyze (experimental instructions on our webpage)
… to its carboxylic acid component (mp.)
…. and its alcohol component alcohol derivative
• Preliminary tests?
• Solubility
• Classification tests
• Derivatives
• Spectra
Amine Derivatives
1. Picrates
2. Benzamides: amine + benzoyl chloride
NH 2
OH
NO 2
NO 2
O 2 N
+
• Preliminary tests?
• Solubility
• Classification tests
• Derivatives
• Spectra
Voodoo Lily Amorphophallus
Amines in plant odors … :
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