What should we know regarding fluorescence? I recall discussing the topic in the past but am unable to find my notes regarding. (When a molecule absorbs the energy of light, it can cause a chemical reaction (photochemistry), or re-emit back as a light of different energy (fluorescence), or “wiggle out” by molecular vibrations to heat. Rigidity of a molecule reduces “wiggling out” the energy, which increases the efficiency of fluorescence. Therefore, we can control fluorescence by affecting the molecule by pH, presence of metals, DNA, etc. That is how many chemical sensors work. - GS).

E1 reactions are not stereoselective, so would the products be present in a racemic mixture like Sn1? (No. Unlike SN1, E1 does not produce a chiral center because the C=C bond is planar. - GS).

So would the addition of acetic anhydride to an amine be acylation? (Yes. It is actually acyl nucleophilic substitution, because half of the anhydride molecule leaves. - GS). Also are there the same issues with acylation as there are with alkylation when trying to make a primary amine or not because acylation is substitution? (No. The C=O group in an acyl blocks the lone electron pair on nitrogen from the second acylation. That is why acylation can be used as a get-around way to avoid the issue with multiple alkylations. Example - Gabriel synthesis. - GS).

Why would the hydrogens attached to the carbons in an ether and amine not be able to be hydrogen bond donors? (The small difference in electronegativity between C and H leads to the low polarity of the C-H bond, which leads to a very small positive charge on H, so it does not interact with the lone electron pair of the H-bond acceptor efficiently. - GS).

For ortho meta para directors, it is the group that is already attached to the ring that “tells” the group that is adding where to go or is it the group that is adding that knows where to add “on its own”? (The group, which is already in the ring, because it participates in the stabilization of the intermediate sigma-complex. The incoming group is separated from the positively charged conjugated system of the sigma-complex by an sp3-carbon, so its influence is minimal.