Question

At normal temperature, iodoform is:
A. Thick viscous liquid
B. Gas
C. Volatile liquid
D. Solid

Answer 1

Hint: Triiodomethane \[{\rm{(CH}}{{\rm{I}}_{\rm{3}}}{\rm{)}}\]is more commonly known as iodoform. From its structural similarity to chloroform, it was named iodoform.

Complete Step by Step Solution:
The methods of preparation of iodoform are:
(1) By the action of iodine and alkali upon ethanol or acetone
\[{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{OH}}\,\,{\rm{ + }}\,\,{{\rm{I}}_{\rm{2}}}\,\, \to \,\,{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{CHO}}\,\,{\rm{ + }}\,\,{\rm{2HI}}\]
\[{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{CHO}}\,\,{\rm{ + }}\,\,3{{\rm{I}}_2}\,\, \to \,\,{{\rm{I}}_{\rm{3}}}{\rm{C}} - {\rm{CHO}}\,\,{\rm{ + }}\,\,3{\rm{HI}}\]
\[\,{{\rm{I}}_{\rm{3}}}{\rm{C}} - {\rm{CHO}}\,\,{\rm{ + }}\,\,{\rm{KOH}}\,\, \to \,\,{\rm{CH}}{{\rm{I}}_{\rm{3}}}\,\, + \,\,{\rm{HCOOK}}\]

Sodium carbonate can also be used in place of potassium hydroxide. With sodium carbonate, the overall reaction is as shown below.
\[{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{OH}}\,\,{\rm{ + }}\,\,4{{\rm{I}}_{\rm{2}}}\,\, + \,\,{\rm{3N}}{{\rm{a}}_{\rm{2}}}{\rm{C}}{{\rm{O}}_{\rm{3}}} \to \,\,{\rm{CH}}{{\rm{I}}_{\rm{3}}}\,\, + \,\,{\rm{HCOONa}}\,\,{\rm{ + }}\,\,{\rm{5NaI}}\,\,{\rm{ + }}\,\,{\rm{2}}{{\rm{H}}_2}{\rm{O}}\,\,{\rm{ + }}\,\,{\rm{C}}{{\rm{O}}_2}\]

(2) By the electrolysis of a solution of ethanol, an iodide and sodium carbonate
This method is used for the industrial preparation of iodoform since it is cheaper. The solution is maintained at \[{\rm{60}} - {\rm{7}}{{\rm{0}}^0}{\rm{C}}\]. During electrolysis, iodine is set free at the anode and sodium hydroxide at the cathode which is subsequently converted into sodium carbonate by passing a current of carbon dioxide. These substances then undergo a reaction with ethanol or acetone to form iodoform.

Iodoform is a yellow crystalline solid whose melting point is \[{\rm{11}}{{\rm{9}}^0}\]. It has a characteristic unpleasant smell. It is insoluble in water but dissolves readily in ethanol, chloroform and ether. In chemical properties, iodoform resembles chloroform. It is, however, less stable than the latter. When heated with an alkali solution, iodoform is hydrolysed to form. Iodoform also undergoes a carbylamine reaction. When warmed with a mixture of aniline and ethanolic \[{\rm{KOH}}\]solution, it reacts in a manner analogous to the corresponding reaction of chloroform.
Hence, it is evident that iodoform is solid.
Therefore, option D is correct.

Note: Iodoform at one time was used extensively as an antiseptic for dressing wounds, but now it has been almost entirely superseded by more efficient compounds.