1- Part Reaction with Sodium Iodide in Acetone- Most of these reactions happened through Sn2 because acetone is polar protic so i t wont disrupt the nucleophile, in this case being I-. I- is a good nucleophile for Sn2 reactions because i t has good polarizability. From the reading, it is known that Sn2 reactions take place mostly with primary alkyl halides and sometimes with secondary halides with a slower rate. Sn2 reactions do not happen with tertiary halides because the leaving group is surrounded by alkyl groups and the nucleophile cannot replace i t. From the results, compounds 1,2,5, and 7 are the primary halides. 2 reacted the fastest but this brings up some questions, as 1 should have technically been the fastest to react as it has a Br leaving group, which is better than Cl- because the conjugate acid is stronger. This mistake most likely came from sheer observations. 5 was not very fast because even with Br, the molecule is not a straight chain which makes part of the molecule hard for the nucleophile to reach. L ike 5, 6 is even harder for the nucleophile to reach because of stereochemistry so although there should have been a reaction, it was not visible. Compounds 3,4, 8 and 9 are all secondary halides so although a reaction should have been seen, i t would have taken a lot longer. Compounds 3 and 4 are extremely similar so they reacted similarly when heat was added to overcome hindrance. L ike 3 and 4, 8 and 9 should have reacted the same
because of similar structures. When head was added, 8 reacted but 9 didn't. 9 is a cyclohexane, so the most probable cause for the lack of reaction was that not enough heat was added to generate a reaction. Because compound 6 is a tertiary halide, there was no reaction, even with heat. The same thing happened with 10 and 11 but like explained in lab, because of their unique shapes, 10 and 11 and incredibly stable and were not going to undergo a reaction, no matter how much heat was added. Part 2- Reaction with ethanolic silver nitrate- Ag+ weakens carbon-halogen bonds, making the leaving group leave to create a carbocation, showing an Sn1 reaction. EtOh is considered a weak nucleophile, but because solvolysis, i t can react well with carbocations. Tertiary and secondary halides react with Sn1 reactions because the carbocation formed is stabilized by hyperconjugation. halides Primary don't react with Sn1 because the primary carbocation that is formed is very high in energy and cant be reached. Although compounds 1 and 2 tu rned foggy, there could not have been a reaction because the compounds are primary straight chain, having too much energy to react. The foggy characteristics were most likely caused by Ag+. Compounds 5 and 6 are also primary halides but they can use Sn1 reactions because the primary carbocation can rearrange with the nearby alkyl groups to
form stable tertiary carbocations, something 1 and 2 lacked. Compounds 3, 4, 8, and 9 react with Sn1 because they form secondary carbocations, which are kind of stable, enough to react. Compounds 6, 10, and 11are tertiary halides so they react the fastest with Sn1 reactions, as i ts easy for the nucleophile to reach the carbocation. Compound 10 reacted a li t tle faster than 11 because like before, Br is a better leaving group than Cl. Conclusion- Several of the predictions made were actually wrong because of obvious oversights. Another helpful tool for predicting is remembering how a molecule has the capacity to rearrange and make tertiary carbocations to become more stable. The lab showed that alkyl halides can react with both Sn1 and Sn2 reactions. Sn1 works best with secondary and tertiary halides but unless rearrangement occurs, primary halides do not use Sn1. Sn2 works best with a good nucleophile and a polar aprotic solvent. Primary works best, secondary can sometimes work and tertiary does not use Sn2 because of hindrance.
1. dry tubes are needed because water molecules will hinder Sn2 reactions. Water is polar protic, which if combined, will form I/D bonds with the I- nucleophile. These bonds will be made all around the
nucleophile, effectively shielding i t from the carbon atom with the leaving group. That's why acetone is used as it is polar aprotic and wont make bonds with the nucleophile. 2. Because the reaction is endothermic, i t means the reaction is taking using heat to move the reaction instead of releasing heat. Since i t is at equilibrium, adding any type of chemical would not help as the percent of product would be the same. The best way to obtain more product would be to simply add more heat to the reaction. By adding heat, the reaction will move in the forward direction. 4.