Question

Which of the following statements is not correct?
A. Methylamine is more basic than $NH_3$.
B. Amines form hydrogen bonds.
C. Ethylamine has a higher boiling point than propane.
D. Dimethylamine is less basic than methylamine.

Answer 1

Hint:All the above statements are on amines therefore let us know all about amines to answer the question. Amines are organic compounds of nitrogen, all the amine sin options are an example of aliphatic amines that is there nitrogen is directly linked to one, two or three same or different alkyl groups.

Complete answer:
All the amines except tertiary amines form intermolecular H bond due to the polar nature of nitrogen but the H-bonds formed are not as strong as formed by –O atom since it has higher electronegativity, it is also why amines are soluble as all the aliphatic amines form H-bonds.
Now the basic strength in amines depends upon the ease with which it accepts a proton to form the ammonium cation i.e basicity depends upon stability of ammonium cation it forms after accepting a proton.
All the aliphatic amines are more basic than ammonia as alkyl groups are electron donating groups as a result the electron density on nitrogen increases and they can donate the lone pair more easily than ammonia. Also dimethyl amine is a secondary amine and methyl amine a primary. Therefore secondary amines are more basic than primary and tertiary amines in aqueous solution due to more +I effect and steric effects.
Similarly amines have higher boiling points than hydrocarbons of comparable molecular masses due to polarity of nitrogen atoms.

Therefore from above we can say the correct option is D as all the other statements are correct.

Note:
Lower aliphatic amines are gases and smell very much like amines. Amines are quite reactive due to the presence of lone pairs on nitrogen and its electronegative difference between nitrogen and hydrogen.