Sn2 Reaction Lab Report

The SN2 reaction requires three qualities: a strong nucleophile, a good, unhindered leaving group, and a polar, aprotic solvent. For our reaction, we have all three bases covered. The nucleophile is an alkoxide, a deprotonated alcohol. Technically, because our alcohol is a phenol, the conjugate base is called a phenoxide. Phenol itself has a pKa of about 10, but our alcohol has more resonance opportunities, so the pKa is down around 8. This is sufficiently acidic for use of weak base like K2CO3 for deprotonation (Scheme 1). The acidic of the aldehyde also helps in purifying the crude product. Our conditions call for excess aldehyde, which we will wash away with base in the work-up. Aside from a good nucleophile, we also have a good, unhindered
Note that not only is this reagent a primary halide, but it also has no _-hydrogens (so no E2 is possible). Finally, our reaction solvent is DMF (N,N-dimethylformamide), a classic solvent for SN2 reactions. With all the conditions in favor of this reaction, it should be no surprise that this reaction works very well

Despite the ease of our reaction, a few comments are in order. Our alkyl halide, cinnamyl bromide, is extremely reactive. As an electrophile, it is activated by something called the phenacyl effect (Reeve J. Am. Chem. Soc. 1954, 76, 2280-2281). The phenacyl effect applies to halides that are adjacent to a _-bond, such as a simple double bond, an aromatic ring, or a carbonyl. The neighboring _-bond stabilizes both SN2 substition and SN1 ionization (Figure