Provide the complete arrow pushing mechanism for the synthesis of

the amide product $($V$).$ This requires the complete mechanism for each

of the three reactions. For the first reaction, you can use generic H$-$A$+$

or H$-$A for the necessary proton transfers. For the second and third

reaction you must properly use the specific molecules present in the

reaction for all proton transfers.

$2.$ Imine formation usually occurs under mildly acidic conditions; however,

no acid is added to this reaction. What is one group present that could

facilitate the necessary proton transfers for this reaction?

$3.$ What is the oxidation state of the carbon of the imine in III and the

oxidation of the same carbon in IV$?$

$4.$ The reaction uses a substoichiometric amount of sodium borohydride

relative to aldehyde and amine starting materials, but the reaction still

gives quantitative yield of product as calculated from the aldehyde or

amine. How is this possible?