Today:
Unknown 1 (review)
aldehyde, ketone, alcohol, phenol
Questions?
Unknown #2:
carboxylic acid, ester, anhydride, amide, amine
(Cl, Br, nitro)
Classification Tests for
Aldehydes and Ketones
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
2,4-dinitrophenylhydrazone (2,4-DNP)
also a good derivative!
→Prepare two good derivatives of each unknown if possible.
Recrystallize from ethanol/water.
Aldehydes and Ketones
• Preliminary tests
To distinguish between aldehydes and ketones:
• Classification tests
• Solubility
• 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
Derivatives
• Preliminary tests
• Solubility
• Classification tests
• Derivatives
Imines:
2,4-dinitrophenylhydrazone
oxime
semicarbazone
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 (positive for 1o, 2o alcohols, aldehydes, 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
Refractive Index
(confirming liquid unknowns)
•
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.
Unknown #2:
carboxylic acid, ester, anhydride, amide,
amine
(Cl, Br, nitro)
Functional groups?
Carboxylic Acids
Anhydrides
Esters
Amides
Amines
Nitro
• Preliminary tests?
• Solubility
• Classification tests
• Derivatives
• Spectra
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?
Carboxylic Acids
Anhydrides
Esters
Amides
Amines
Nitro
• Preliminary tests
• Solubility?
• Classification tests
Solubility Tests
• Derivatives
• Spectra
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
Carboxylic Acids
• Classification tests
Good mp.s (consider recrystallization)
• Derivatives (not done)
• Spectra
Neutralization Equivalent (titration)
experimental instructions on our webpage
RCO2H + NaOH
RCO2(–) Na(+)aq. + H2O
Derivatives (we do not do them in the lab):
Convert carboxylic acid into acid chloride first, then into amides
1.
+ HCl
2.
Define carboxylic acid by: mp., neutr. equivalent, an ester and its bp.
• Preliminary tests?
Esters
• Solubility
• Classification tests
Classification Test
• Derivatives
• Spectra
a hydroxamic
acid
Deep-red
to purple
Compare with known ester!
Derivatives for Esters
Hydrolyze (experimental instructions on our
webpage)
• Preliminary tests?
• Solubility
… to its carboxylic acid component (mp.)
• Classification tests
• Derivatives
• Spectra
…. and its alcohol component
alcohol derivative
Amine Derivatives
• Preliminary tests?
• Solubility
1. Picrates
• Classification tests
OH
NH
O 2N
2
NO
• Derivatives
2
+
• Spectra
NO
2
2. Benzamides: amine + benzoyl chloride
Amines in plant odors … :
Voodoo Lily
Amorphophallus
Next time:
• Conclusion Unknown 2
• Inert Compounds:
Alkanes
Aromatic Hydrocarbons
Alkyl halides
• UV spectra
• MiniQuiz on today’s class