CHM145L Organic Chemistry 1 Laboratory 2nd Quarter SY 2012-2013
Melting Point and Boiling Point of Organic Compounds 1
Estopace, Edgie , Tayag, Carlo A.
2
Estopace, Edgie, School of Chemical Engineering, Chemistry an d Biotechnology, Mapua Institute of Technology; 2Tayag, Carlo A., CHM145L/A21, School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology
1
ABSTRACT In this experiment, melting point and boiling point of organic compounds is to be determined. The main objective of the experiment is to determine the effects of various factors like intermolecular forces of attraction, purity, and branching to the melting and boiling point range of organic compounds. Thus, the structural theory was given an emphasis in the experiment as well as in this paper. Also, different ways and means were used in the determination of melting points and boiling points of different organic compounds. The apparatus used and procedure that were followed are the one written in the laboratory manual. Some revisions were added to lessen the time spent in the experiment and for the student to finish the experiment on time. On the other hand, most or almost of the results are the one the student expected to arrive with. However, some of the results are not that close to what are expected. All in all, melting points and boiling points were determined after the experiment with respect to the chemical structures of each organic compound. Keywords: melting point, boiling point, organic compound, chemical structures
INTRODUCTION Chemical structures of different organic compounds affect its different properties such as chemical properties (e.g. susceptibility to reactions with certain reagents, types of reactions they undergo with reagents, the rates a t which the react, the extent of these reactions) and physical properties (e.g. boiling points, melting points, solubility in polar and nonpolar solvents). This is called the structural theory. In this experiment, two physical properties: melting point and boiling point will be focused on. With this experiment, students are expected to learn how chemical structures of different organic compounds affect its properties. The purpose of the experiment is to determine the effects of chemical structures such as intermolecular forces of attraction, geometric isomerism, purity, and branching to the melting point and boiling point of test compounds given.
plate and micro test tubes. We also used Bunsen burner to save time because heating the Thiele tube with glycerol is much faster than heating it in the hot plate. Procedures in the laboratory manual were also followed with some revisions. We used new glycerol instead of cooling it down and reusing it because it also saves time. RESULTS
I.
Melting Point A. Structural Effect a. Intermolecular Forces Attraction COMPOUND T1 T2 MELTING 0 0 0 ( C) ( C) POINT ( C)
of
MATERIALS AND METHODS In the determination of melting point of test compounds given, Thomas-Hoover Melting Point Apparatus, capillary tubes were used. The procedure we used in the determination of melting point is exactly the same as the one provided in the laboratory manual except that we put all of the samples in the Thomas-Hoover Apparatus at the same time. We did this to consume less time. Regarding the second experiment, the determination of boiling point, we used Thiele tubes, capillary tubes, thermometers, hot
Experiment 01│ Group No.
5│ 10-15-12
Benzoic Acid
104
131
117.5
Benzoin
114
134
124
Naphthalene
123
175
149
Salicylic Acid
165
180
172.5
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CHM145L Organic Chemistry 1 Laboratory 2nd Quarter SY 2012-2013
Urea
120
151
135.5
Note: Results in Naphthalene were unexpected and maybe wrong. b. Geometric Isomers Substituent COMPOUND T1 T2 MELTING 0 0 0 ( C) ( C) POINT ( C) Maleic Acid
135
148
141.8
Fumaric Acid
250
303
276.5
or
B. Branching COMPOUND T1 T2 0 0 ( C) ( C) n-butyl alcohol sec-butyl alcohol tert-butyl alcohol
BOILING 0
POINT ( C)
118
118
118
101
102
101.5
79
82
80.5
DISCUSSION
B. Effect of Purity on Melting Point Range COMPOUND T1 T2 MELTING 0 0 0 ( C) ( C) POINT ( C) Pure Urea
120
151
135.5
Impure Urea
82
91
86.5
II.
Boiling Point by a Micro Method A. Intermolecular Forces Attraction COMPOUND T1 T2 BOILING 0 0 0 ( C) ( C) POINT ( C) n-Butanol
113
120
116.5
2-Butanone
82
110
96
n-Pentane
84
91
87.5
Propanoic Acid n-Hexane
136
142
139
64
72
68
of
In the experiments with regards to intermolecular forces of attraction, the physical properties of a compound were determined. It is often difficult to use the molecular structure alone to predict a precise melting point or boiling point for a compound. However, a few simple trends will allow us to compare compounds to each other in a relative way, for example, to predict which compound will boil at a higher temperature. In this case, compound with higher attractive force has the higher melting point. Regarding the experiments of effect of purity on melting point, I can say that an impure compound has lower melting point range. Lastly, experiment with regards to branching shows that the compound with highest number of branch will have the lowest boiling point. CONCLUSIONS AND RECOMMENDATIONS Based on the experiment, the melting point and boiling point of a specific organic compound is relative to its chemical structure. structure. I recommend to the next student student who will perform this experiment to be more careful because many compounds that were used are volatile which may worsen the result and may even harm them.
Note: N-heptane was used instead of n-pentane.
Experiment 01│ Group No.
5│ 10-15-12
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CHM145L Organic Chemistry 1 Laboratory 2nd Quarter SY 2012-2013
REFERENCES
1. Baluyut, J.Y., and De Castro, K. Organic Chemistry Laboratory Manual for Chemistry Students, Part 1, 1-8 2. Klein, D. (2012). Organic Chemistry. United States: John Wile & Sons, Inc.
Experiment 01│ Group No.
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