Q62E - Organic Chemistry (Mcmurry)

Question

Thiamin diphosphate (TPP), a derivative of vitamin B1 required for glucose metabolism, is a weak acid that can be deprotonated by a base. Assign formal charges to the appropriate atoms in both TPP and its deprotonation product.

Step-by-Step Solution

Answer

Formal charge on nitrogen is 1

The formal charge on Oxygen is -1

Step 1: Definition of Formal Charge

The formal charge (F.C) can be defined as the difference number of valence electrons and number of electrons present in the Lewis structure.

$\mathrm{F}.\mathrm{C}=\left[\mathrm{V}\left(\mathrm{electrons}\right)-\mathrm{L}\left(\mathrm{electrons}\right)\right]$

V = valence shell

L = electrons present according to Lewis structures

Step 2: Assign formal charge to the respective atomic species

$$\begin{gathered} \text{F.C = }\left[\text{V}\left(\text{electrons}\right)\text{ - L}\left(\text{electrons}\right)\right] \\ \text{F.C on Oxygen = 6 - 7 = - 1} \\ \text{F.C on Nitrogen = 5 - 4 = 1} \end{gathered}$$

Step 3: Assign the formal charge to atoms

Assign the formal charge to the atomic species present in the chemical reaction where it is required

                                          Reactant (on left hand side

                                             Product (on right hand side