Q10.89CP - Chemistry: Molecular Nature Of Matter And Change

Question

The Murchison meteorite that landed in Australia in 1969 contained 92 different amino acids, including 21 found in Earth organisms. A skeleton structure (single bonds only) of one of these extraterrestrial amino acids is shown below. Draw a Lewis structure, and identify any atoms with a nonzero formal charge

Step-by-Step Solution

Answer

Lewis’s structure 

+1 charge on  ${{\mathbf{NH}}_3}^{+}$and -1 charge on${\mathbf{COO}}^{-}$ add up to zero net charge.

 

Step 1: Definition

The charge that would be present on an atom in a molecule if all of the bonding electrons were distributed equally is known as the formal charge of the atom.

Formula:

 

 $\mathbf{FC}\mathbf{=}\mathbf{V}\mathbf{-}\frac{B}{2}\mathbf{-}\mathbf{N}$

FC= formal charge 

V = number of valence electrons 

N= number of non-bonding valence electrons

B=total number of bonds electrons in bonds

 

Step 2: Lewis’s structure

The name of given amino acid is serine. The Lewis structure of serine is drawn below. it has two terminals. One is N- terminal (amino group present) and another is C- terminal (carboxylic group present). In the Lewis structure N-terminal has ammonium ion and C-terminal has carboxylate ion. Both terminals are attached with a central carbon atom. And central atom is also bonded with a hydrogen atom and a ethyl group.

 

Step 3: Formal charges

Formal charge on N atom $\mathbf{=}\mathbf{5}\mathbf{-}\frac{8}{2}\mathbf{-}\mathbf{0}\mathbf{=}\mathbf{+}\mathbf{1}$

Formal charge on O atom  $\mathbf{=}\mathbf{6}\mathbf{-}\frac{2}{2}\mathbf{-}\mathbf{6}$$\mathbf{=}\mathbf{-}\mathbf{1}$