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redravin40 · 11-30-2003, 08:47 PM

MY best effort considering I know little about the chem processes you are describing.

2-methyl-2-butanol can be dehydrated by reacting it with sufficient quantities of sulfuric acid to yield two possible alkene products. The products of the reaction can be separated from the equilibrium solution by means of fractional distillation. Statistical and thermodynamic analysis of the two possible products (2-methyl-2-butene and 2-methyl-1-butene) produces contradictory pictures of which product should be favored. This experiment was, therefore, conducted and its products analyzed by two methods. Infrared (IR) spectroscopy was performed to confirm that the products were the two expected butenes. Gas chromatography (GC) was performed to determine the actual percent composition of each of the products.

The two theoretical percent compositions and the experimentally determined percent compositions were then compared and analyzed.
IR spectroscopy is a widely used and nondestructive technique for the experimental determination of molecular structure. IR analysis can provide data about the functional groups of a molecule, and a fingerprint of the molecule as a whole. This form of analysis is generally used in conjunction with other data, because it has several limitations. Most important, IR analysis cannot determine the exact number of atoms in each functional group. Furthermore, the data gathered by IR equipment show only the polar bonds in a molecule.For the purpose of this experiment, IR data was collected to insure that both expected products were, indeed, present. The IR spectrum created by the computer for the product sample provided five valuable pieces of data.

Two of the peaks were in the expected regions for a tri-substituted alkene, i.e., (2-methyl-2-butene) (Dr. McMillen, 2003). One peak was at the 803 wave number (cm-1) and the second was at the 1678 wave number (cm-1), showing an alkene C-H bend and an alkene C=C stretch, respectively. There were also two peaks in the expected regions for a di-substituted alkene, i.e., (2-methyl-1-butene) (Dr. McMillen, 2003). One peak was at the 887 wave number (cm-1) and the second was at the 1652 wave number (cm-1), showing an alkene C-H bend and an alkene C=C stretch, respectively. The fifth informative peak on the IR spectrum was located at the 3040 wave number (cm-1) and was located in the expected region for an alkene C-H stretch. With this data, it is possible to conclude that the sample contained both expected alkenes. Determination of the quantities of each alkene in the sample required the results of a GC analysis.

GC analysis is performed to analyze the quantities of molecules present in a sample. This is accomplished by first separating the molecules in a sample by their chirality, polarity, and/or boiling point. After separation, a detector determines the quantities of each component of the mixture relative to each another. For this test, the sample butenes were separated using a J&W scientific DB1701 capillary column, which separated them according to boiling points. The lower boiling component would be the first to leave the column.

The sample was then passed through a flame ionization detector (FID), which detected the relative quantities of each component. A computer running Star Chromatography Workstation was then used to graph and analyze the data.
The GC analysis of the butenes yielded two identifiable peaks. The first peak was determined to be that of 2-methyl-1-butene, because it was the lower boiling component of the mixture. 2-methyl-1-butene has a boiling point of 31.16 C and 2-methyl-2-butene's boiling points is 38.57 C.

Because we did not know the response factor (a constant) for each of our butenes, we were forced to assume in our calculations that the response factors of each butene were approximately the same. The calculation for percent yields of each butene was therefore simplified to the area in counts of the peak in question, divided by the total area in counts of all peaks identified. Performing this calculation for each butene's peak yielded a value of 9.2269% composition for 2-methyl-1-butene and 90.5555% composition for 2-methyl-2-butene. The next step was to compare the GC data to the statistical and thermodynamic expectations.

The dehydration of 2-methyl-2-butanol is a three-step process as diagramed below:

Steps
1- Acid/Base Reaction:
2- Heterolytic Bond Cleavage 3- Acid/Base Reaction

The alkene products of the dehydration of 2-methyl-2-butanol were analyzed by GC and IR spectroscopy. The IR data confirmed that both a trisubstituted and a disubstituted alkene were present in the product, as expected. The GC analysis provided data allowing the percent yields of the two alkenes to be calculated. The data yielded by IR and GC analysis of the alkene products was then compared to the statistical and thermodynamic expectations for the reaction. This comparison showed that although 2-methyl-2-butene is statistically favored, the thermodynamic stabilities of the two products were, in fact, more important in determination of an actual yield. Therefore, 2-methyl-2-butene was favored as the major product due to its greater thermodynamic stability.

also moving this to Knowledge.

11-30-2003, 08:47 PM	#3 (permalink)
redravin40 Loser Location: With Jadzia	MY best effort considering I know little about the chem processes you are describing. 2-methyl-2-butanol can be dehydrated by reacting it with sufficient quantities of sulfuric acid to yield two possible alkene products. The products of the reaction can be separated from the equilibrium solution by means of fractional distillation. Statistical and thermodynamic analysis of the two possible products (2-methyl-2-butene and 2-methyl-1-butene) produces contradictory pictures of which product should be favored. This experiment was, therefore, conducted and its products analyzed by two methods. Infrared (IR) spectroscopy was performed to confirm that the products were the two expected butenes. Gas chromatography (GC) was performed to determine the actual percent composition of each of the products. The two theoretical percent compositions and the experimentally determined percent compositions were then compared and analyzed. IR spectroscopy is a widely used and nondestructive technique for the experimental determination of molecular structure. IR analysis can provide data about the functional groups of a molecule, and a fingerprint of the molecule as a whole. This form of analysis is generally used in conjunction with other data, because it has several limitations. Most important, IR analysis cannot determine the exact number of atoms in each functional group. Furthermore, the data gathered by IR equipment show only the polar bonds in a molecule.For the purpose of this experiment, IR data was collected to insure that both expected products were, indeed, present. The IR spectrum created by the computer for the product sample provided five valuable pieces of data. Two of the peaks were in the expected regions for a tri-substituted alkene, i.e., (2-methyl-2-butene) (Dr. McMillen, 2003). One peak was at the 803 wave number (cm-1) and the second was at the 1678 wave number (cm-1), showing an alkene C-H bend and an alkene C=C stretch, respectively. There were also two peaks in the expected regions for a di-substituted alkene, i.e., (2-methyl-1-butene) (Dr. McMillen, 2003). One peak was at the 887 wave number (cm-1) and the second was at the 1652 wave number (cm-1), showing an alkene C-H bend and an alkene C=C stretch, respectively. The fifth informative peak on the IR spectrum was located at the 3040 wave number (cm-1) and was located in the expected region for an alkene C-H stretch. With this data, it is possible to conclude that the sample contained both expected alkenes. Determination of the quantities of each alkene in the sample required the results of a GC analysis. GC analysis is performed to analyze the quantities of molecules present in a sample. This is accomplished by first separating the molecules in a sample by their chirality, polarity, and/or boiling point. After separation, a detector determines the quantities of each component of the mixture relative to each another. For this test, the sample butenes were separated using a J&W scientific DB1701 capillary column, which separated them according to boiling points. The lower boiling component would be the first to leave the column. The sample was then passed through a flame ionization detector (FID), which detected the relative quantities of each component. A computer running Star Chromatography Workstation was then used to graph and analyze the data. The GC analysis of the butenes yielded two identifiable peaks. The first peak was determined to be that of 2-methyl-1-butene, because it was the lower boiling component of the mixture. 2-methyl-1-butene has a boiling point of 31.16 C and 2-methyl-2-butene's boiling points is 38.57 C. Because we did not know the response factor (a constant) for each of our butenes, we were forced to assume in our calculations that the response factors of each butene were approximately the same. The calculation for percent yields of each butene was therefore simplified to the area in counts of the peak in question, divided by the total area in counts of all peaks identified. Performing this calculation for each butene's peak yielded a value of 9.2269% composition for 2-methyl-1-butene and 90.5555% composition for 2-methyl-2-butene. The next step was to compare the GC data to the statistical and thermodynamic expectations. The dehydration of 2-methyl-2-butanol is a three-step process as diagramed below: Steps 1- Acid/Base Reaction: 2- Heterolytic Bond Cleavage 3- Acid/Base Reaction The alkene products of the dehydration of 2-methyl-2-butanol were analyzed by GC and IR spectroscopy. The IR data confirmed that both a trisubstituted and a disubstituted alkene were present in the product, as expected. The GC analysis provided data allowing the percent yields of the two alkenes to be calculated. The data yielded by IR and GC analysis of the alkene products was then compared to the statistical and thermodynamic expectations for the reaction. This comparison showed that although 2-methyl-2-butene is statistically favored, the thermodynamic stabilities of the two products were, in fact, more important in determination of an actual yield. Therefore, 2-methyl-2-butene was favored as the major product due to its greater thermodynamic stability. also moving this to Knowledge.