When we did a SN1 reaction forming t-amyl chloride from t-amyl alcohol and HCl (cleaning the crude sample with NaCl and NaHC03, using CaCL2 as a drying agent) we observed a low boiling fraction around 40 degrees Celsius during distillation.
Question: What might be present in this fraction and should it be included in the purified product. WHy or Why not?
The alcohol boils at 102 C.
The chloride boils at 85-86 C.
So with that much difference in boiling with a fraction at about 40 C, I don't think it should be included with the product. That large a boiling point different must mean the 40 C fraction is something different. Could it be 2-methyl-2-butene or a similar product? That has a boiling point of 39 C. Check my data to make sure I didn't misread a table.
That makes sense because in this SN1 reaction a E1 reaction competes with the carbocation intermediate and forms a side product...which is 2-methyl-2-butene.
But I don't understand why or why not the fraction is included in the product. Is it just because their boiling points are so far apart? Hence, what criteria are used to determine if its included or not? When would something be included?
If you are distilling something to purify it, why would you want to add something different and deliberately contaminate a product?
The low boiling fraction observed during distillation in the purification of t-amyl chloride could potentially contain impurities or by-products. To determine what might be present in this fraction, we can consider the reaction mechanism and properties of the starting materials and products.
In the SN1 reaction to form t-amyl chloride from t-amyl alcohol and HCl, the alcohol undergoes nucleophilic substitution. In this process, the hydroxyl group (-OH) of the alcohol is replaced by a chloride ion (-Cl).
During the reaction, the formation of t-amyl chloride is the desired outcome. However, there are a few possible by-products or impurities that may be present in the reaction mixture. Some of these can be:
1. Excess t-amyl alcohol: It is possible that not all of the starting alcohol completely reacts, and some of it may be present in the low boiling fraction.
2. HCl: Since HCl is used as a reactant, a small amount of unreacted HCl may also be present in the fraction.
3. By-products: Depending on the conditions of the reaction, there might be side reactions or rearrangements leading to the formation of undesired substances. These by-products could end up in the low boiling fraction.
4. Water: Since both t-amyl alcohol and HCl can contain traces of water, it may also be present in the fraction.
As for whether the low boiling fraction should be included in the purified product, it is important to consider the purity requirements of the final product and the expected properties of the impurities present.
If the impurities present in the low boiling fraction are likely to affect the desired properties or functionality of t-amyl chloride, it is generally recommended to exclude the fraction from the final product. However, if the impurities are expected to be minimal and will not significantly impact the desired properties, it may be acceptable to include the fraction in the purified product.
To make a final decision, it is crucial to conduct further analysis of the low boiling fraction, such as via gas chromatography-mass spectrometry (GC-MS), which can identify the specific compounds present and their concentrations. Based on the analysis results, a judgment can be made on whether to include or exclude the fraction from the purified product.