Which will be the least stable resonating structure?

A. C H2 = CH - C+ H - C- H - NH2
B. C- H2 - C+ H - CH = CH - NH2
C. C- H2 - CH = CH - CH = N+ H2
D. C H2 = CH - C- H - CH = N+ H2

To determine the least stable resonating structure, we need to consider the stability of the resulting ions and the distribution of charge within each structure.

Let's evaluate each option:

A. C{H2} = CH - C+H - C-H - NH2
In this structure, we have a positive charge on one carbon atom (C+) and a negative charge on another carbon atom (C-). This separation of charges makes this structure relatively unstable.

B. C-H2-C+H - CH = CH - NH2
Here, we have a positive charge on one carbon atom (C+) and a negative charge on another carbon atom (C-). Similar to option A, this structure also has charge separation and is relatively unstable.

C. C-H2-CH = CH - CH = N+H2
In this structure, we have a positive charge on a nitrogen atom (N+) and a negative charge on a carbon atom (C-). While this still involves charge separation, it is somewhat less unstable than options A and B because the charges are on different types of atoms.

D. C{H2} = CH - C-H - CH = N+H2
In this structure, we have a positive charge on a nitrogen atom (N+) and a negative charge on a carbon atom (C-). Similar to option C, this structure has charge separation, but it is relatively more stable because the charges are on different types of atoms.

So, the least stable resonating structure among the given options is option A because it has charge separation with positive and negative charges on adjacent carbon atoms, which is less stable compared to having charges on different types of atoms.