North Carolina A & T State University Chemistry Lab Report

Using robust details and ample evidence, create a reflection essay that describes 4 learning objectives you met while performing this experiment.  View the learning objectives from the lab manual provided and select four to focus your writing on.

Virtual Lab Manual
Functional Groups and Basic
Chemical Tests
Synopsis
Functional … what? In this simulation, you will learn the very basics of functional groups
within organic chemistry, and perform simple chemical tests to validate their presence.
Organic chemical compounds Tooth trouble
You will start off by meeting with Simon, who’s having trouble with a terrible toothache. He’s
gotten some painkillers, but from a source he’s not entirely sure he can trust. Perhaps you
can help him figure out if it’s alright for him to take the painkillers?
Prepping for the real deal
In the lab, you join forces with Dr. One, who will support and test you on your mission. After
suiting up for the lab, you dive straight into the first experiment: the bromine test. Here you
need to show Dr. One that you’re comfortable when it comes to simple chemical tests—so
the produced results in your main mission can be trusted!
Validation by chemical tests
You then move on to deal with the main mission: Salicylic acid. First, you need to figure out
which functional groups are in this organic compound. Once that’s sorted, you move to the
fume hoods again to test whether these groups are indeed present in your sample from
Simon. Dr. One might have a little extra challenge waiting for you though.
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An update for Simon
Armed with your findings, you will return to Simon to share what you’ve learnt about the
contents of the painkillers he got. It will be tricky to get the chemical tests right, but luckily
you can repeat the experience if you want to practice more. Will you be able to solve the
functional group challenge?
Learning Objectives
At the end of this simulation, you will be able to…
● Give examples of functional groups of organic compounds and their reactions
● Determine the presence of specific functional groups by carrying out simple chemical
tests
● Investigate the functional groups present in salicylic acid by performing a series of
chemical tests
Techniques in Lab
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Bromine test for unsaturated hydrocarbons
Ceric Ammonium Nitrate test for alcohols and phenols
Sodium bicarbonate test
Theory
The nature of organic compounds
Organic chemistry is the study of organic compounds and their structure, properties, and
reactions. Organic compounds are chemicals that are based on the element carbon, and
most often they would also contain bonds between carbon and hydrogen. Methane, a
hydrocarbon, shown in Figure 1, is one of the simplest organic compounds.
Figure 1: Structure of methane, a simple organic compound.
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Many organic compounds contain elements other than carbon and hydrogen, typically oxygen
and nitrogen, but there can also be other groups such as phosphorus or halogens.
Some carbon compounds are not considered to be organic, e.g. carbonates and carbon oxides
like carbon monoxide and carbon dioxide. These types of compounds are regarded as
inorganic.
Functional groups
Functional groups are the parts of a molecule responsible for its reactivity. Different
functional groups give rise to different reaction types in organic chemistry.
Functional groups can be a specific arrangement of carbon and hydrogen, e.g. a double bond,
or can also include other elements. The most common elements in organic compounds
besides carbon and hydrogen are oxygen and nitrogen. Other examples of elements are
phosphorus and halogens. You can see the functional groups of salicylic acid in Figure 2.
Figure 2: The functional groups of salicylic acid. Purple = phenol; green = carboxylic acid; blue
= phenyl.
Positive and negative controls
In chemistry, controls are a way to validate the results of your experiment. A positive control
should show a positive result in a test, whereas a negative control should show a negative
result. If the result is not as expected, you cannot trust that the test was performed
correctly for your actual experiment.
Ceric ammonium nitrate test
The ceric ammonium nitrate test is a way to examine a solution for the presence of either
alcohols or phenols. In solution, the orange-yellow ceric ammonium nitrate makes a complex
with the alcohol or phenol, which results in a color change in the solution. Alcohols cause a
red color change, whereas phenols induce a more dark-red to dark-brown color change,
depending on the phenol involved.
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The reaction is as follows:
Materials
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Test tubes
Test tube rack
Ceric ammonium nitrate solution
Compound to be tested
Safety information
Ceric ammonium nitrate is a strong oxidizer, corrosive, an irritant, and an environmental
hazard. Contact with other materials may cause a fire. It is harmful if swallowed and eye
contact may result in permanent eye damage. It causes eye, skin, and respiratory tract
irritation.
Procedure
1.
Make a solution of the organic compound dissolved in a suitable solvent. Put 1 mL in a
test tube.
2. Add a few drops of ceric ammonium nitrate solution.
3. If the solution becomes a red color then an alcohol group is present in the organic
compound.
4. The red color disappears if:
○ You keep the reaction mixture for some time.
○ You add an excess of ceric ammonium nitrate solution. Therefore, avoid using
an excess of ceric ammonium nitrate solution.
Sodium bicarbonate test
Sodium hydrogen carbonate, also known as sodium bicarbonate, reacts with acidic solutions
to form carbon dioxide, which is released as gas from the solution, resulting in so-called
brisk effervescence. Sodium hydrogen carbonate can be used to test for carboxylic acids. If
effervescence occurs, then an acid group is present.
The reaction is as follows:
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Phenol is a weak acid meaning it dissolves in sodium hydroxide solution but does not
dissolve in sodium hydrogen carbonate solution. Stronger acids, such as carboxylic acids,
dissolve in both solutions. This can be useful for separating mixtures of acids.
Materials
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Test tubes
Test tube rack
Sodium hydrogen carbonate solution
Compound to be tested
Safety
Acidic solutions are corrosive. Sodium hydrogen carbonate is an irritant.
Procedure
1.
Put 2 mL of a saturated aqueous solution of sodium hydrogen carbonate in a clean
test tube.
2. Add a few drops of the liquid compound or a few crystals of the solid compound to it.
Add the compound slowly so that effervescence is clearly visible.
3. Brisk effervescence of carbon dioxide indicates the presence of a carboxylic acid
group.
Bromine test
The bromine test is used to test for an unsaturated carbon carbon bond, such as an alkene
or alkyne. The test uses a type of chemical reaction called addition, where a reactant, here
bromine, is added to an organic compound to break a double or triple bond.
For example the addition of bromine to but-2-ene:
Bromine has an orange-brownish color when in solution, so the color of the solution is lost
when an alkene or alkyne is present for bromine to react with. Bromine will also react with
aromatic compounds, such as phenol, but it can’t react with alkanes as they contain only
single bonds, and therefore there is no color change when these are mixed. Benzene can
react with bromine in the presence of a catalyst, but not without a catalyst since it is not
reactive enough. Phenol is more reactive than benzene so can react with bromine without a
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catalyst. This is because the alcohol group donates electron density into the delocalized
benzene ring.
Materials
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Test tubes
Test tube rack
Carbon tetrachloride
Chloroform
Bromine water
Compound to be tested
Safety information
Bromine is corrosive, toxic, and an environmental hazard. Bromine causes eye and skin burns,
as well as digestive and respiratory tract burns. It may be fatal if inhaled and is a strong
oxidizer. Contact with other material may cause a fire. Corrosive to metal. Carbon
tetrachloride is toxic. Chloroform is harmful. This test should be performed at room
temperature.
Procedure
1.
Dissolve 0.1 g or 5 drops of organic compound in 2 mL of carbon tetrachloride. If you
do not have carbon tetrachloride, a solvent such as chloroform or water can be used
to dissolve the organic compound.
2. Add 2% solution of bromine water drop by drop with continuous shaking.
3. If the bromine solution becomes colorless then there is an unsaturated carbon carbon bond in
the organic compound. This test should be confirmed with the baeyers test.
Hydrocarbons in water
Hydrocarbons are nonpolar, which means that they generally don’t mix well with water.
Simple hydrocarbons that are liquid at room temperature, such as hexane, have a lower
density than water, and therefore forms a separate layer on top of water. These layers are
called phases. This two-phase system can be used for e.g. extracting organic compounds
from a water sample into hexane, which can have many advantages in analytical chemistry.
Alcohols and phenols
In organic chemistry, alcohols are a functional group where a hydroxy (-OH) group is bound to
a saturated carbon. If the hydroxy group is bound to an aromatic ring, the functional group is
called a phenol. See examples of an alcohol and phenol in Figure 6. Note that phenol is both
the name of the functional group, and the simplest compound within this group.
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Figure 6: Structures of ethanol and phenol.
Aromatic rings
Aromatic rings are a common group in organic chemistry. They are planar ring systems, where
a series of double bonds make the molecule conjugated, which means that the p orbitals
used for the π bonds overlap with p orbitals on both sides of each carbon atom. Figure 7
shows benzene, one of the simplest aromatic compounds. Though commonly drawn like this,
each carbon in the compound is actually bonded in the exact same way to both of its
neighbors.
Figure 7: The structure of benzene, one of the simplest aromatic compounds.
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