Simple Procedure for writing Lewis Structures for methanimine CH2NH- #25

A simple procedure for writing Lewis structures is given in a previous article entitled “Lewis Structures and the Octet Rule”.  
Several worked examples relevant to this procedure were given in previous posts please see the Sitemap - Table of Contents (Lewis Electron Dot Structures).

Let us consider the case of  methanimine, CH₂NH . Methanimine can form the simplest aminoacid, glycine, when it reacts with either hydrogen cyanide and then with water, or formic acid. It has been detected even in other galaxies like Arp220 in 2008.

 

Step 1: Connect the atoms with single bonds. The central atom is the carbon atom.

Step 2: Calculate the # of electrons in π bonds (multiple bonds) using  formula (1): 

Where n in this case is 5 since CH₂NH consists of five atoms.

Where V = (1 + 1 + 4 + 5 + 1 ) = 12  

Therefore, P = 6n + 2 – V = 6 *2 + 2 – 12 = 2   Therefore,  there is one double bond and the structure in Step 1 is has one double bond.

 

Step 3 & 4: The Lewis structure for CH₂NH is as follows:

Figure 1: Lewis structure for methanimine.

Simple Method for writing Lewis Structures for bromate BrO3- #24

A simple procedure for writing Lewis structures is given in a previous article entitled “Lewis Structures and the Octet Rule”. Relevant worked examples were given in the following articles: Examples #1, #2, #3 , #4, #5, #6,  #7,  #8, #9, #10, #11, #12, #13, #14,  #15, #16, #17, #18, #19, #20, #21 , #22 and  #23.

Let us consider the case of  BrO₃^-. Bromates are formed by many different ways in municipal drinking water, The most common is the reaction of Br^- with ozone:

                                                           Br^-  + O₃ →   BrO₃^-

In waters containing bromide (Br^-), such as those found in coastal regions subject to salt water intrusion, a disinfection by-product of the ozonation treatment of the water is the bromate ion BrO₃^-.
 The bromate ion is very carcinogenic with an estimated lifetime cancer risk 1:10000 for a concentration of 5 ppb. Several methods are used for the determination of bromate in drinking waters including an LC-ICP-MS method.
 

Step 1: Connect the atoms with single bonds. The central atom is the bromine atom.

Step 2: Calculate the # of electrons in π bonds (multiple bonds) using formula (1): 

Where n in this case is 4 since BrO₃^- consists of four atoms.

Where V = (7 + 6 + 6 + 6 ) – (-1) = 26  

Therefore, P = 6n + 2 – V = 6 *4 + 2 – 26 = 0     So, there are no π electrons in BrO₃^- and the structure in Step 1 is the Lewis structure. However, let us see the charge on the atoms.

Step 3 & 4: The Lewis structure for BrO₃^-  including charge is as follows:

Figure 1: Lewis structures for BrO₃^- . Structure 3 has the most reasonable distribution of formal charges.