Name the functional group of the following compounds:
$(i) \ R-COOH$
$(ii) \ R-COOR'$
$(iii) \ R-OH$
$(iv) \ R-X$

(N/A) $(i)$ The functional group $-COOH$ is known as the Carboxylic acid group.
$(ii)$ The functional group $-COOR'$ is known as the Ester group.
$(iii)$ The functional group $-OH$ is known as the Alcohol group.
$(iv)$ The functional group $-X$ (where $X = F, Cl, Br, I$) is known as the Halide group,and the compound is called an Alkyl halide or Haloalkane.