The first question. Some electronic effects should be considered. For example, acetanilide has a yoke of carbonyl carbon (sp2) and n electrons, which is relatively stable, but the electron density on n will be reduced, and the alkalinity will also be reduced. Phthalimide is more terrible, with two carbonyl yokes ... and then N- methylaniline, and methyl should be an electron-donating group, so the basicity of imino group is enhanced. ..........................................................................................................................
The second question. I really don't understand this ... from the electronic point of view, let's consider the substituents attached to the carbon atoms of unsaturated bonds. If there is an electron-donating effect, then unsaturated bonds are relatively stable (I heard a teacher say that electrons are like glue ...), and vice versa, they are easily cracked ... probably so.
The third question. At least five-membered rings are formed after condensation, otherwise the tension is too great.
The fourth question. All aldehydes or ketones with the structural formula R'CH2-CO-R(R can also be aryl) can undergo halogen-imitating reaction. At the same time, ethanol and methyl secondary alcohol are oxidized to carbonyl compounds under this reaction condition, so halogen imitation reaction can also occur. See /view/ 1398323.htm#4.
The fifth question. I only know that anhydrous calcium chloride will form a complex with ethanol, which seems to be CaCl2 2C2H5OH, and so should other lower alcohols.
I wrote this on a whim, hoping to help you. ....................................................................................................................................................................