Immex Problem
Title: “Finding Carbon’s Neighbors”
Problem Description: A student is working on updating his lab’s inventory when he
comes across a bottle in which the label is no longer legible. There are 24 compounds on
his list that cannot been found in the lab; therefore, this compound is most likely one of
these 24. The student decides to use the proton NMR to quickly characterize the sample,
but to his dismay the NMR is not operating properly. Unfortunately, he had forgotten to
order pH paper so he could not carry out that simple test. He was left with determining the
identity using laboratory methods to characterize the compound’s functional group and
physical properties. Help the student determine the identity of the unknown compound
using the tests available. Each test will cost you 2 pts. You are starting with 120 pts. An
incorrect answer will cost you 15 pts. You are allowed two attempts at solving this
problem. Each item viewed in the library will cost you 3 pts.
Library
Functional Group Tests
Alcohols
1. Chromic Acid Test – a primary or secondary alcohol will reduce the orange – red
chromic acid/sulfuric acid reagent to an opaque green or blue suspension of Cr (III)
salts.
2. Lucas Test – a test in which concentrated HCl is added with ZnCl2.
a. Tertiary – alkyl halide formation is identified by the formation of an insoluble
layer or emulsion. Takes less than a minute for this reaction to occur.
b. Secondary – same result with longer time requirement for reaction (5-10 min)
c. Primary – no reaction
3. Iodoform Test – a yellow precipitate of iodoform appears within 15 minutes.
Aldehydes/Ketones
1. Reaction with 2,4-dinitrophenylhydozine – formation of a large amount of yellow to red,
insoluble 2,4-dinitrophenylhydrozone indicates a positive result.
2. Oxidation of Aldehydes with Chromic Acid – a primary or secondary alcohol will reduce
the orange – red chromic acid/sulfuric acid reagent to an opaque green or blue
suspension of Cr (III) salts.
3. Iodoform Test – a yellow precipitate of iodoform appears within 15 minutes.
4. Tollens Test – a silver mirror or colloidal silver appears in the test tube.
Alkenes
1. Reaction with Bromine – alkenes react with bromine and the characteristic red-brown
color of bromine disappears. For most alkenes, this reaction occurs so rapidly that the
solution never acquires a red color until the reaction is complete.
2. Oxidation with Potassium Permanganate – the purple color of the permanganate
solution is replaced within 2 – 3 minutes by a brown precipitate of manganese
dioxide.
Alkyl Halides
1. Beilstein Test – a blue-green flame indicates the presence of a halogen.
2. Reaction with Silver Nitrate – the formation of a precipitate of (silver halide) is a
positive indication of the presence of a halide.
3. Reaction with Sodium Iodide in Acetone – the formation of an obvious precipitate
(NaCl or NaBr) is a positive test
Aromatic Hydrocarbons
1. Ignition Test – Many alkanes and their substituted derivatives burn with a clean
yellow or bluish flame, whereas most aromatic compounds burn with a smoky flame.
2. Reaction with Aluminum Chloride/Chloroform – a color change of the powder and
the solution indicates a positive test
Amines
A reaction with 1.5 M HCl is a positive test for an amine.
Carboxylic Acids
A reaction with a base such as NaOH or NaHCO3 is often a positive test for a carboxylic
acid.
Acyl Chloride
Reaction with Silver Nitrate – the formation of a precipitate of (silver halide) is a
positive indication of the presence of a halide.
Esters
Hydroxamic Acid Test – a positive test is a blue red color.
Ethers
Ferrox Test – a red to reddish purple color appears if the unknown contains oxygen.
Phenols
i. Reaction with Bromine/Water – disappearance of the organic bromine color,
accompanied by a precipitate is a positive test.
ii. Reaction with Ferric Chloride – most phenols react with ferric chloride to form red to
blue ferric phenolate complexes.
Low MW Amines
Low MW Carboxylic Acids
Solubility Tests
Low MW Neutrals
soluble
e
Compound
H2O
soluble
NaHCO3
Insoluble
soluble
Insoluble
2.5 M NaOH
Strong Acids
(Carboxylic Acids,
Phenols, Acyl Halides)
Weak Acids
(Most Phenols)
Bases (Amines)
Insoluble
soluble
1.5 M HCl
Very Weak
Bases
Insoluble
soluble
Insoluble
Neutral
Compounds
Menu Options
(1.) Chromic Acid Test
(2.) Tollens Test
(3.) Reaction with Bromine/Water
(4.) Reaction with Silver Nitrate
(5.) Hydroxamic Acid Test
(6.) Ignition Test
(7.) Reaction with Sodium Iodide in Acetone
(8.) Ferrox Test
(9.) Reaction with Ferric Chloride
(10.) Reaction with Aluminum Chloride/Chloroform
(11.) Lucas Test
(12.) Iodoform Test
(13.) Reaction with 2,4-dinitrophenylhydozine
(14.) Oxidation with Potassium Permanganate
(15.) Solubility Tests
(16.) Odor
(17.) Boiling/Melting Point
(18.) Physical State
(19.) Inventory List
(20.) Color
--------------------------------------------------For the "Finding C's Neigh." problem, I have one minor change that I would
like to make. When the compound is soluble in water, I would like for the
solubility results for HCl and NaOH to say Not Available. Here is a list
of the compounds that are soluble in water:
(1.) Acetamide
(2.) Pyrrolidine
(3.) Chloroacetic Acid
(4.) Maleic Acid
(5.) 1-chloro-2-propanol
(6.) 2-Pentanol (Perhaps for this compound we should say that it is
slightly soluble...because it is not completely soluble).
***For the Prussian Blue Test...any compound with an N should have a dark
blue precipiate.****
I counted 7 cases that should have a positive Prussian Blue Test.
3 - nitroacetophenone
2 - nitro - 1 - methoxy benzene
4 - nitro phenol
2 - aminoheptane
Acetanilide
Pyrrolidine
Acetamide
***For the ferrous hydroxide test...any compound with an -NO2 group should
have a dark red precipitate. Only three compounds should give a postive
result for the ferrous hydroxide test. For the other compounds you can
simply say that there is no reaction or no change.
***The three compounds that should give a positve test ferrous hydroxide
test are:
3 - nitroacetophenone
2 - nitro - 1 - methoxy benzene
4 - nitro phenol