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Carbocations: Factors affecting their Stability

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A carbocation is a species where a carbon atom bonds to three carbon atoms and has a positive charge. Carbocations are electron deficient species and therefore very reactive and unstable . Anything which donates electron density to the electron-deficient center will help to stabilize them. Factors that stabilize them are the following:  Neighboring carbon atoms (inductive effect) Neighboring carbon-carbon multiple bonds (resonance effect) Neighboring atoms with lone pairs (resonance effect) How carbocations are stabilized by neighboring carbons atoms? The stability of carbocations decreases as the number of carbons attached to the C+ decreases. That means that tertiary carbocations are more stable than secondary that in turn are more stable than primary (Fig. 1). Fig. 1: Carbocation stability increases as methyl substitution increases around the electron deficient carbon C+. The methyl groups (-CH 3 ) are electron donating and therefore stabilize the positive charge (inductive effe
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Polyprotic Acids / pH Calculation

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Home > Weak Acids and Bases – Calculate the pH of a weak acid (a general equation) > Solving Weak Acid and Weak Base pH problems > Weak Acid Weak Base pH calculation solved example > Weak Acid Weak Base pH calculation solved example > Cubic Equation Calculator for Weak Acid-Base Equilibria > Polyprotic Acids / pH Calculation Polyprotic Acids / pH Calculation A large number of acids can give two or more protons on ionization ( dissociation ) and these are referred to as polyprotic acids . For example, with sulfurous acid (H 2 SO 3 ) we have the successive ionizations: Fig. I.1: Stepwise dissociation of sulphurous acid (H 2 SO 3 ) A polyprotic acid always dissociates in a stepwise manner, one proton at a time. Note that the acid dissociation constants are labelled k a1 and k a2 . The numbers on the constants refer to the particular proton of the acid that is ionizing. Thus, k a1 always refers to the equilibrium involving removal of the first prot
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Ionic Radius Periodic Table of the Elements

Ionic Radius Periodic Table of the Elements Home > Fundamental Physical Constants - Chemical - Physical - Thermochemical Data > Ionic Radius Periodic Table of the Elements Periodic Table with Ionic Radius   Ion size plays an important role in determining the structure and stability of ionic solids, the properties of ions in aqueous solution, and the biological effects of ions. As with atoms, it is impossible to define precisely the sizes of ions . Ionic radii are determined from the measured distances between ion centers in ionic compounds. A table of ionic radii is given below.   Table 1: Periodic Table with Ionic Radii (Å) of the elements 1 2 3 4 5 6 7 H 1.46             Li 0
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