Hello! In advance, I want to excuse if I am not clear enough somewhere, as I'm Swedish.
I need help with my lab assignment. In my textbook, I am taught about substitution reactions SN1 and SN2, as well as elimination reactions E1 and E2. What it didn't mention is how the location of a halogen in an alkane has an impact on the reaction rate, or how different chemical properties of a halogen impacts the reaction rate.
My objective in the first and second trial of the experiment is to identify what is nucleophilic and electrophilic in the reaction, the haloalkane that reacts fastest/slowest. In the first trial during the reaction, a chemical bond in the haloalkane is broken, and the difference in reactivity could be due to how polar the bond is, but it could also be due to the strength of the bond. In the second trial, I have to identify which bromoalkane that reacts fastest/slowest. Also, to identify what the solvent is during the reaction, and in what way a choice of solvent could affect the type of reaction mechanism. I.e., what mechanism should occur? Which bromoalkane should react the fastest, given the answer? Which one should react the slowest?
Also, if you happen to know any sources of error with the experiment, please share.
Without further ado, here's the instructions of my experiment:
The purpose of this experiment is to compare the reaction rate of substitution in 1-chlorobutane, 1-bromobutane and 1-iodobutane as well as 1-bromobutane, 2-bromobutane and 2-bromo-2-methylpropane. Study how the reaction rate for substitution reactions is impacted by the chemical properties and location of the halogens in the alkanes. Use ethanol to ensure that the haloalkane dissolves, and can react with the water molecules. Aqueous silver nitrate is also added to the haloalkane, and the halide leaving group combines with a silver ion to form a silver halide precipitate.
For the experiment, I have two trials. First trial is to place four test tubes in a water bath that maintains 50°C, and let the test tubes remain there for about 10 minutes, so that they reach the temperature of the water bath. Then add 1 cm³ of the heated silver nitrate solution to each of the test tubes 1, 2 and 3 as simultaneously as possible, and took note of the time.ResultsTable 1
picture of the result from the first experiment. From left to right: 1-bromobutane, 1-chlorobutane, and 1-iodobutane in reaction with silver nitrate solution.
In the second trial, the experiment was performed at room temperature, where two test tubes were made in which 1cm³ of ethanol is added to both test tubes, and 2 drops of 1-bromobutane are added to test tube 1, and 2 drops of 2-bromo-2-methylpropane are added to test tubes 2. Then, I add 1 cm³ of silver nitrate solution to each of the three tubes as simultaneously as possible, taking note of the time. The tubes were observed for about 5 minutes, and the observations were recorded.Table 2
picture of the result from the second experiment. From left to right: 1-bromobutane, 2-bromobutane, and 2-bromo-2-methylpropane in reaction with silver nitrate solution.