(N/A) Oxidation of primary alcohol compounds: Primary alcohols can be oxidized to carboxylic acids using strong oxidizing agents like potassium permanganate $(KMnO_4)$ in acidic,basic,or neutral media,or potassium dichromate $(K_2Cr_2O_7)$ in acidic medium,or Jones reagent $(CrO_3 + H_2SO_4)$.
General reaction:
$RCH_2OH \xrightarrow{[O]} RCOOH$
Examples:
$1$. $CH_3(CH_2)_8CH_2OH \xrightarrow{CrO_3-H_2SO_4} CH_3(CH_2)_8COOH$
$2$. $CH_3CH_2OH \xrightarrow{K_2Cr_2O_7-H_2SO_4} CH_3COOH$
$(b)$ Oxidation of aldehyde compounds: Aldehydes are easily oxidized to carboxylic acids using mild oxidizing agents like Tollen's reagent or stronger agents like $KMnO_4$ or $HNO_3$.
General reaction:
$R-CHO \xrightarrow{[O]} RCOOH$
Examples:
$1$. $CH_3CHO \xrightarrow{[O]} CH_3COOH$
$2$. $C_6H_5CHO \xrightarrow{[O]} C_6H_5COOH$