Introduction
This experiment was performed in order to compare the ability of bromine atoms to react with hydrogen atoms of different classifications. The experiment compared aromatic, aliphatic and benzylic hydrogen atoms of primary, secondary, and tertiary classifications. The time it took for the reaction to occur was measured and compared between the different hydrocarbons. This rate of reaction was used to determine the reactivity of the various hydrogen atoms on the hydrocarbons with bromine.
Data and Results
Toluene, which contained primary benzylic hydrogen atoms, exhibited a reaction time of 7 seconds. Ethylbenzene, which contained secondary benzylic hydrogen atoms, exhibited a reaction time of 2 seconds. Tert-butylbenzene, which contained primary alipathic hydrogen atoms, exhibited a reaction time of greater than 46 minutes. Cyclohexane, which contained secondary aliphatic hydrogen atoms, exhibited a reaction time of greater than 46 minutes. Methylcyclohexane, which contained tertiary aliphatic hydrogen atoms, exhibited a reaction time of 36 minutes. These reaction rates were measured by observing the disappearance of color from the solution.
Discussion and Conclusion
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For this reaction to occur, light and bromine must both be present.
The light provides the energy to break the bond between the two bromine atoms, creating the bromine radicals. The energy required to break the bond is known as the bond dissociation energy. The bromine radicals can then attack the hydrocarbons, creating carbon radicals and HBr. These carbon radicals in turn attack the bromine that is not in radical form, which results in the creation of the R-Br products and regeneration of bromine radicals. This allows the reaction to continue though propagation. Different hydrogen atoms demonstrate different reactivity depending on the stability of the different transition states that are formed with the carbon radical
intermediates. Benzylic hydrogen atoms are more reactive than aromatic and aliphatic hydrogen atoms because the radical can be stabilized via resonance through the pi bonds of the benzene ring. Resonance delocalizes the charge, which creates a more stable transition state. Aliphatic hydrogen atoms are bound to sp3 hybridized carbon atoms. Aromatic hydrogen atoms are bound to sp2 hybridized carbon atoms that make up an aromatic ring. These two groups of hydrogen atoms have similar reactivity as their transition states have similar stability. Hydrogen atoms are further categorized as primary, secondary or tertiary. Primary hydrogen atoms are bound to a carbon atom that is bound to one other carbon atom. Secondary hydrogen atoms are bound to a carbon atom that is bound to two other carbon atoms. Tertiary hydrogen atoms are bound to a carbon atom that is bound to three other carbon atoms. As such, tertiary hydrogen atoms are the most reactive as the radical charge can be delocalized to the other surrounding carbon atoms and primary hydrogen atoms are the least reactive as the charge cannot be delocalized. This theory was demonstrated by the experiment. Ethylbenzene, with secondary benzylic hydrogen atoms and thus the most stable transition state, exhibited the fasted reaction rate. Toluene, with primary benzylic hydrogen atoms, still exhibited a faster reaction time than the aliphatic and aromatic hydrogen atoms but slower than the secondary benzylic hydrogen atom. Tert-butylbenzene, with primary aliphatic hydrogen atoms, and cyclohexane, with secondary aliphatic hydrogen atoms, exhibited the slowest reaction times owing to their less stable transition states. Methylcyclohexane, with tertiary aliphatic hydrogen atoms, exhibited a slower reaction time than the benzylic hydrogen atoms but faster than the primary and secondary aliphatic hydrogen atoms.
As a final point, the unknown secondary alcohol α-methyl-2-naphthalenemethanol had the R-configuration since it reacted the fastest with S-HBTM and much slower with R-HBTM. TLC was a qualitative method and ImageJ served as a quantitative method for determining which reaction was the faster esterification. Finally, 1H NMR assisted in identifying the unknown from a finite list of possible alcohols by labeling the hydrogens to the corresponding peaks.
The goal of this experiment is to determine which products are formed from elimination reactions that occur in the dehydration of an alcohol under acidic and basic conditions. The process utilized is the acid-catalyzed dehydration of a secondary and primary alcohol, 1-butanol and 2-butanol, and the base-induced dehydrobromination of a secondary and primary bromide, 1-bromobutane and 2-bromobutane. The different products formed form each of these reactions will be analyzed using gas chromatography, which helps understand stereochemistry and regioselectivity of each product formed.
In a small reaction tube, the tetraphenylcyclopentadienone (0.110 g, 0.28 mmol) was added into the dimethyl acetylene dicarboxylate (0.1 mL) and nitrobenzene (1 mL) along with a boiling stick. The color of the mixed solution was purple. The solution was then heated to reflux until it turned into a tan color. After the color change has occurred, ethanol (3 mL) was stirred into the small reaction tube. After that, the small reaction tube was placed in an ice bath until the solid was formed at the bottom of the tube. Then, the solution with the precipitate was filtered through vacuum filtration and washed with ethanol. The precipitate then was dried and weighed. The final product was dimethyl tertraphenylpthalate (0.086 g, 0.172mmol, 61.42%).
The goal of this two week lab was to examine the stereochemistry of the oxidation-reduction interconversion of 4-tert-butylcyclohexanol and 4-tert-butylcyclohexanone. The purpose of first week was to explore the oxidation of an alcohol to a ketone and see how the reduction of the ketone will affect the stereoselectivity. The purpose of first week is to oxidize the alcohol, 4-tert-butylcyclohexanol, to ketone just so that it can be reduced back into the alcohol to see how OH will react. The purpose of second week was to reduce 4-tert-butylcyclohexanol from first week and determine the effect of the product's diastereoselectivity by performing reduction procedures using sodium borohydride The chemicals for this lab are sodium hypochlorite, 4-tert-butylcyclohexanone
The goal of this lab is to exemplify a standard method for making alkyne groups in two main steps: adding bromine to alkene groups, and followed by heating the product with a strong base to eliminate H and Br from C. Then, in order to purify the product obtained, recrystallization method is used with ethanol and water. Lastly, the melting point and IR spectrum are used to determine the purity of diphenylacetylene.
In a separate beaker, acetone (0.587 mL, 8 mmol) and benzaldehyde (1.63 mL, 16 mmol) were charged with a stir bar and stirred on a magnetic stirrer. The beaker mixture was slowly added to the Erlenmeyer flask and stirred at room temperature for 30 minutes. Every 10 minutes, a small amount of the reaction mixture was spotted on a TLC plate, with an eluent mixture of ethyl acetate (2 mL) and hexanes (8 mL), to monitor the decrease in benzaldehyde via a UV light. When the reaction was complete, it was chilled in an ice bath until the product precipitated, which was then vacuum filtrated. The filter cake was washed with ice-cold 95% ethanol (2 x 10 mL) and 4% acetic acid in 95% ethanol (10 mL). The solid was fluffed and vacuum filtrated for about 15 minutes. The 0.688 g (2.9 mmol, 36.8%, 111.3-112.8 °C) product was analyzed via FTIR and 1H NMR spectroscopies, and the melting point was obtained via
Abstract: This week we experimentally determined the rate constant k for the reaction 2HCl (aq) +Na2S2O3 (aq) → S (s) + SO2 (aq) + H2O (l) + 2NaCl (aq). In order to do this the average reaction time was recorded in seconds during two trials. The data from the experiment shows this reaction is in the first order overall: rate=.47s-1 [HCl]0 [Na2S2O3]1. These findings seem to be consistent with the expected results
Benzyl bromide, an unknown nucleophile and sodium hydroxide was synthesized to form a benzyl ether product. This product was purified and analyzed to find the unknown in the compound. A condenser and heat reflux was used to prevent reagents from escaping. Then the solid product was vacuum filtered.
Ensure gloves are worn at all times when handling strong acids and bases within the experiment of the preparation of benzocaine. 4-aminobenzoic acid (3.0g, 0.022 moles) was suspended into a dry round-bottomed flask (100cm3) followed by methylated sprits (20 cm3). Taking extra care the concentrated sulphuric acid of (3.0 cm3, 0.031 moles) was added. Immediately after the condenser was fitted on, and the components in the flask were swirled gently to mix components. It should be ensured that the reactants of the concentrated sulphuric acid and the 4-aminobenzoic acid were not clustered in the ground glass joint between the condenser itself and the flask. In order to heat the mixture to a boiling point, a heating mantle was used and then further left for gently refluxing for a constituent time of forty minutes. After the duration of the consistent forty minutes the rou...
The Absorption Spectrum of Chlorophyll Water + carbon dioxide → glucose + oxygen 6H2O + 6CO2 → C6H12O6 + 6O2 Absorption Spectrum An absorption spectrum shows which wavelength of light a molecule absorbs. Action Spectrum An action spectrum shows the effect of each wavelength of light on the rate of photosynthesis The absorption spectrum of chlorophyll is very similar to the action spectrum of photosynthesis. This is evidence that chlorophyll absorbs light for photosynthesis. The Light and Dark Reaction 1) The light reaction light 6H2O→12H + 3O2 Light splits water into hydrogen ions and oxygen.
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