ORGANIC CHEMISTRY
LAB REPORT 01
EXPERIMENT TITLE: BOILING POINTS AND MELTING POINTS
ABSTRACT
The
chemical structures of different organic compounds affect different properties
such as chemical properties (adaptability of reactions to certain reactions,
types of reactions with reactions, the rates at which they react, the magnitude
of these reactions) and physical properties ( boiling point, melting points,
solubility in polar and non polar solvents). This is called structural theory. In this experiment, melting point and boiling
point of organic compounds are to be determined. The main goal of similarity is
to determine the effects of various factors such as the intermolecular forces
of attractiveness, purity, and branching on a range of heating and boiling
organic compounds . In addition, different methods and methods have been used
to determine the melting and boiling points of various organic compounds. The
apparatus used and the procedure followed were the ones written in the
laboratory . On the other hand, most or nearly all of the outcomes the we
expects to come with. Melting and
boiling points were generally determined after the event for the chemical
structures of each organism compounds.
INTRODUCTION
An
organic compound is defined as any compound containing carbon and hydrogen
(also known as "hydrocarbons") or a derivative compound. The branch
of science that deals with the scientific study of the structure, properties
and reactions of hydrocarbons and their derivatives is called organic
chemistry.
The
physical properties of compounds, such as melting and boiling, can be useful
information that will help identify a sample or establish its purity.
The
melting point of a substance is the temperature at which the material changes
from a solid to a liquid state and the boiling point is the temperature at
which it changes from liquid to solid. set up. Since this requires
that the intermolecular forces that hold the solid together have to be
overcome, the temperature at which melting occurs will depend on the structure
of the molecule involved - an example of the relationship between structure and
properties. Hence, different compounds tend to have different melting points .A
pure, nonionic, crystalline organic compound usually has a sharp and
characteristic melting point (usually 0.5-1.0C range). A mixture of very small
amounts of miscible impurities will produce a depression of the melting point
and an increase in the melting point range. Consequently, the melting point of
a compound is a criterion for purity as well as for identification.
Boiling
is used to characterize a new organic liquid, and boiling point information
helps to compare one organic liquid to another, as is the process of
identifying an unknown organic substance. It is useful to compare boiling
points to melting points. The process of determining the boiling point is more
complex than the process for the melting point in that it requires more
material. Moreover, because impurities have less impact on it, it is not as
good as an indicator of purity. Understanding the differences in the melting
and boiling points of organic compounds involves understanding trends.
The
most important thing to consider here is that melting points and boiling points
show the strength of forces between molecules. The more they stick together,
the more energy it will take to separate them into liquid and gas molecules,
respectively. There are 3 important trends to consider. 1. The relative
strength of the intermolecular forces is: hydrogen bonding & dipole dipole & ; Van der Waals or London
scattered forces. The impact of each of these attractive forces will depend on
the functional groups present. 2. Melting / boiling points increase as the
number of carbon increases. 3. Branches reduce melting / boiling points of
organic compounds .
OBJECTIVES
1.
To determine the
boiling point of a liquid
2.
To determine the
melting point of a solid
MATERIALS AND METHOD
Materials
Solids:
· Benzoic
acid
· Benzophenone
Liquids:
· Methanol
· Ethanol
· Isopropyl
alcohol
Oil
bath
Capillary
tubes
Thermometer
Rubber
bands
Methods:
A. Boiling points
- The apparatus was assembled as illustrated in the lab manual .
- The
boiling points of the three liquids, methanol, ethanol and isopropyl alcohol
were determined.
- 2
ml of methanol was poured into a clean dry test tube and the tube was secured
to a ring stand so that the surface of the methanol was slightly below the oil
level and the tip of the thermometer was about 1 cm above the surface of the
methanol.
- The mineral oil was heated. The temperature of the oil bath was measured with another thermometer. The temperature of the oil bath was not allowed to go above 80˚C. The temperature was recorded when the temperature reading remained constant at one value.
- Steps 3 and 4 were repeated to the other two samples of ethanol and isopropyl alcohol. For the ethanol sample, the temperature of the oil bath was not allowed to exceed above 90˚C. The bath was allowed to cool to about 75˚C before the third sample of oil was placed. For the isopropyl alcohol, the temperature wasn’t allowed to exceed above 100˚C.
A. Melting
points
1. The
apparatus was assembled as illustrated in the lab manual .
2. Melting
points of Benzoic acid and Benzophenone were measured.
3. For
each sample, a separate capillary tube, sealed from one end was used. In order
to fill the capillary tube, a small pile of solid was made on the watch glass
and the open end of the capillary tube was forced through the crystals to get
some sample into the tube. Then the sealed end was tapped lightly on the table
top to get the sample down into the sealed end. This procedure was repeated
until about 0.5 cm of the sample was collected in the capillary tube.
4. A
small rubber band was used to attach the capillary tube to the thermometer.
5. The
thermometer and the capillary tube was placed in the oil bath as shown in
diagram 02.
6. As
the oil was heated slowly, it was stirred by raising and lowering the wire
loop.
7. The
temperature was recorded when the crystals first began to melt and also the
temperature at which the last crystal melted.
RESULTS
Results:
A. Boiling
points
|
Sample |
Handbook values of
boiling points, ℃ |
Experimental values
of boiling points , ℃ |
|
Methanol |
64.70 |
65.00 |
|
Ethanol |
78.37 |
76.00 |
|
Isopropyl alcohol |
82.50 |
81.00 |
B. Melting
points
|
Sample |
Handbook
values of melting points, ℃ |
Experimental
values of melting point range, ℃ |
|
Benzophenone |
49.00 |
48.00-50.00
|
|
Benzoic acid |
122.30 |
120.00-123.00
|
DISCUSSION
The
main target of the experiment was to determine the boiling and the melting
points of few organic compounds. The boiling points of methanol, ethanol and isopropyl
alcohol and the melting point range of benzophenone and benzoic acid were
determined.. with the results we can conclude that pure solids have fixed
melting points, but can occur over a range of temperatures when impurities are
present. Moreover, pure liquids have constant boiling points whereas a
substance will boil over a range of temperatures if impurities are present.
Two
experiments were conducted in order to determine the boiling point and the
melting point of organic compounds. In the first trial, boiling points of the
organic compounds methanol, ethanol and isopropyl alcohol were determined. Results
were observed as the boiling point of
methanol was 65.00°C, ethanol - of 76.00°C and isopropyl alcohol - 81.00°C. In the second trial, melting points
of the organic compounds Benzophenone and Benzoic acid were determined. The
melting point range of Benzophenone was observed as 48.00-50.00°C and a melting
range of 120-123°C was observed for Benzoic acid. All these values had a slight
deviation when compared with the standard boiling point . values may have
slight changes apart from handbook values due to the impurities of the
compounds .
According to the observations we can This
means that the boiling points of these have increased due to the more impurities
present in the compounds , also if a higher pressure was exerted on the liquid,
it can result in a higher boiling point. The boiling points of different
materials depend on the intermolecular forces
present between the atoms.
During
this experiment, the most suitable heat source was the oil bath. In this
experiment, mineral oil was used as it can fit into temperatures greater than
the boiling point of water. As mineral oil contains a mixture of long chain
alkenes, it is considered as combustible
if the oil was heated too strongly, the hot oil may spatter and if any
moisture touches the oil, the oil may smoke or ignite.
The
liquids used in this experiment are flammable. Therefore, all the liquids must
be kept away from open flame. Safety precautions
should be taken when conducting this
experiment.
Post lab questions
1.
Why
must you allow the oil bath to cool between melting point determination?
In order to avoid some practical issues which
can be arose when conducting the experiment for ex : when previous melting
point is much higher than the following melting point . also as we didn’t allow it to cool so it may cause to receiving
incorrect readings .
a.
If
you performed a melting point experiment on the same compound in San Francisco
and on top of Mt.Everest, would your result differ? Explain.
The melting point should be differed because of that the atmospheric pressure of San Francisco and the on top of Mt.Everest are different. At the high atmospheric pressure, the melting point get the high value than at low atmospheric pressure because the atmospheric pressure has positive relationship with melting point.
2. Cocaine
melts at 980C and glucose melts at 1460C. As chemist for
the government it is your task to quickly identity the content the three vials.
One contains pure cocaine, another pure glucose, and the third a mixture of
cocaine and glucose. How you accomplish your assignment?
3 melting points from specific samples are obtain first ant then each sample should be labelled and the melting temperature for each sample should be recorded. After that the recorded temperatures are evaluated and compared with relevant temperature. 980C for octane and 1460C are defined as glucose and one which represents a range of temperature identified as mixture of cocaine and glucose.
3.
Suppose
you determine the melting point of cortisone (a hormone) to be 2300C.
your two neighbors obtain values of 2260C and 2330C. Why
might their values differ from your value?
The samples may differ according to their
impurity which could lower or higher the range for the melting point of the
compound.
APENDIX
Figure 1; Thermometer that used for measure temp.
Figure 2; measuring the boiling point
REFERENCES
1. Schofstall, A.; Gaddis B.; Drueling, M.; Meling Point; Microscale and Miniscale Organic Chemistry Laboratory Experiments, McGraw-Hill, (2011), 28-34 and 83 - 91.
2. Mohrig, J.R.; Alberg,
D.G.; Hofmeister, G.E.; Schatz, P.F.; Hammond, C.N.; Laboratory Techniques in Organic Chemistry;
Freeman, New York, 2014, 174-176; 206-211; 291-308
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