Potassium is placed where it is based on its properties and it's reactivity. It's also placed there based on it's atomic number. 
        
             
        
        
        
Answer:
Four possible isomers (1–4) for the natural product essramycin. The structure of compound 1 was attributed to essramycin by 1H NMR, 13C NMR, HMBC, HRMS, and IR experiments.
Explanation:
Three synthetic routes were used to prepare all four compounds (Figure 2A). All three reactions utilize 2-(5-amino-4H-1,2,4-triazol-3-yl)-1-phenylethanone (5) as the precursor, whereas each uses different esters (6–8) to construct the pyrimidinone ring. Isomer 1 was prepared by reaction A, which used triazole 5 and ethyl acetoacetate (6) in acetic acid. This was the reaction used in syntheses of essramycin by the Cooper and Moody laboratories.3,4 Reaction B produced compound 2 (minor product) and compound 3 (major product), which were separated chromatographically. This reaction allowed reagent 5 to react with ethyl 3-ethoxy-2-butenoate (7) in the presence of sodium in methanol, under reflux for 24 h. Compound 4 was prepared by reaction C, which was obtained by reflux of 5 and methyl 2-butynoate (8) in n-butanol.
 
        
             
        
        
        
The difference between a distraction and a reaction is.... A distraction is a thing that prevents someone from giving full attention to something else. A reaction is a action performed or a feeling experienced in response to a situation or an event.
        
                    
             
        
        
        
Answer : 
The correct answer for primary component of phosphate buffer at pH = 7.4 is H₂PO₄⁻ and HPO₄²⁻ . 
<u>Buffer solution :</u>
 It is a solution of mixture of weak acid and its conjugate base OR weak base and its conjugate acid . It resist any change in solution when small amount of strong acid or base is added . 
<u>Capacity of a good buffer : </u>
A good buffer is identified when pH = pKa . 
 From Hasselbalch - Henderson equation which is as follows : 
![pH = pka + log \frac{[A^-]}{[HA]}](https://tex.z-dn.net/?f=pH%20%3D%20pka%20%2B%20log%20%5Cfrac%7B%5BA%5E-%5D%7D%7B%5BHA%5D%7D)
If [A⁻] = [HA] ,
pH = pka + log 1 
pH = pKa 
This determines that if  concentration of  weak acid  and its conjugate base are changed in small quantity , the capacity of  buffer to maintain a constant pH is greatest at pka .  If the amount of [A⁻] or [HA] is changed in large amount , the log value deviates more than +/-  1M and hence pH . 
Hence Buffer has best capacity at pH = pka .
<u>Phosphate Buffer : </u>
Phosphate may have three types of acid-base pairs at different pka ( shown in image ). 
Since the question is asking the pH = 7.4 
At pH = 7.4 , the best phosphate buffer will have pka near to 7.4 .
If image is checked the acid - base pair  " H₂PO₄⁻ and HPO₄²⁻  has pka 7.2 which is near to pH = 7.4 .
Hence we can say  , the primary chemical component of phosphate buffer at pH = 7.4  is H₂PO₄⁻ and HPO₄²⁻  .