recall the reactions by which carboxylic acids can be produced: (a) oxidation of primary alcohols and aldehydes with acidified \( K_2Cr_2O_7 \) or acidified \( KMnO_4 \) and refluxing (b) hydrolysis of nitriles with dilute acid or dilute alkali followed by acidification (c) hydrolysis of esters with dilute acid or dilute alkali and heat followed by acidification

recall the reaction (reagents and conditions) by which esters can be produced: (a) the condensation reaction between an alcohol and a carboxylic acid with concentrated \( H_2SO_4 \) as catalyst