Ch. 3 - Acids and BasesSee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins

The holy grail of acid-base chemistry is to be able to draw the mechanism and predict the equilibrium for an acid-base reaction. Believe it or not, you’re ready to do this. 

STEP 1. Identify the acid and base

  • Many times charges or a known acid will be present (+) = Acid (–) = Base
  • If you see no charges, dissociate ALL spectator ions, these are the cations Li+, Na+, K+  and Ca+
  • If both compounds are still neutral, assign the one with the lowest pKa as the acid.

STEP 2. Label the conjugate acid and base. Remember:

  • Acids LOSE their most acidic proton to become conjugate bases
  • Bases GAIN a proton to become conjugate acids

STEP 3. Compare the acidity/pKa of the acid to the conjugate acid. The equilibrium will favor the side with the weaker acid (arrow towards the highest pKa).

That’s all there is to it! Watch me solve the first example so you can get the hang of it. 

Concept #1: The 3 steps for determining the direction of acid and base equilibrium.  

Would the following reaction go to the right or left? Label All ALL species. Draw arrows in the correct direction.

Example #1: Would the following reaction go to the right or left? Label ALL species. Draw arrows in the correct direction.

Would the following reaction go to the right or left? Label All ALL species. Draw arrows in the correct direction.

Example #2: Would the following reaction go to the right or left? Label ALL species. Draw arrows in the correct direction.

Additional Problems
Write a chemical equation for the reaction of 1-butanol with each of the following:  (a) Sodium amide (NaNH2)
Which ionization state predominates at thermodynamic equilibrium? Based on the conclusion, predict whether the substance is a solid, liquid or gas at room temperature (Note: (CH3)2CHNH2 and C2H5COOH are both liquids at room temperature.)
Predict the favorable direction of the two following acid base equilibria: A) I→  and II→ B) I→ and II← C) I← and II← D) I← and II→
Crude extracts from the ginkgo tree, Ginkgo biloba, have been used for centuries to alleviate symptoms associated with asthma. There are four principal components of Ginkgo extracts, called ginkgolide A, B, D, and M. During E. J. Corey’s classic synthesis of ginkgolide B, compound  1 was converted into compound 5 (J. Am. Chem. Soc. 1988, 110, 649–651): (b) Draw a mechanism for the conversion of  1 to 3 and explain why this step is irreversible.
In the rounded boxes, write the products for each of the following acid-base reactions. a) These reactions will be in equilibrium, and the equilibrium can favor one side or the other or be balanced (i.e. nearly equal). Indicate which side of the reaction is favored in the equilibrium either by use of arrows ⇌ or writing on one side of the reaction, “favored”. b) Draw the curved arrows to show the flow of e- for each of these reactions.
Which structure corresponds to the predominant form of this molecule near pH 7?
Each of the following acid–base reactions involves substances found in Table 1.8. Use the pKa data in the table to help you predict the products of the reactions. Use curved arrows to show electron flow. Predict whether the equilibrium lies to the left or to the right and calculate the equilibrium constant for each reaction. 
Each of the following acid–base reactions involves substances found in Table 1.8. Use the pKa data in the table to help you predict the products of the reactions. Use curved arrows to show electron flow. Predict whether the equilibrium lies to the left or to the right and calculate the equilibrium constant for each reaction. 
Each of the following acid–base reactions involves substances found in Table 1.8. Use the pKa data in the table to help you predict the products of the reactions. Use curved arrows to show electron flow. Predict whether the equilibrium lies to the left or to the right and calculate the equilibrium constant for each reaction.   
Each of the following acid–base reactions involves substances found in Table 1.8. Use the pKa data in the table to help you predict the products of the reactions. Use curved arrows to show electron flow. Predict whether the equilibrium lies to the left or to the right and calculate the equilibrium constant for each reaction. 
Each of the following acid–base reactions involves substances found in Table 1.8. Use the pKa data in the table to help you predict the products of the reactions. Use curved arrows to show electron flow. Predict whether the equilibrium lies to the left or to the right and calculate the equilibrium constant for each reaction. 
Determine the side of the reaction that is favored for each reaction: Following letters express the direction of equilibrium: R = Right L = Left  
Does the equilibrium lie to the left or right? (Choose one)  
Does the equilibrium lie to the left or right? (Choose one)    
Which of the following can deprotonate acetylene? You are given the pKa values of the conjugated acid in parentheses.  A. Only I B. Only I and II C. Only I and III D. Only II and III E. Only II and IV
Use the reaction below to answer A-C.
Would ethanol (CH 3CH2OH) be a suitable solvent in which to perform the following proton transfer? Explain your answer:
Indicate the shift of the acid-base equilibriums below by enlarging one of the equilibrium arrows.    
Consider the reactions below and answer the following questions: a. Provide the major organic products. b. Show the mechanism. You will need to redraw the molecules to show relevant bonds and lone pairs. c. Determine which way the equilibrium lies and why.
Which reactions proceed forward?
HA has a pKa of 15, while HB has a pKa of 5. Draw the equilibrium that would result upon mixing HB with NaA. Does the equilibrium favor formation of HA or of HB?
For each reaction below, draw the mechanism (curved arrows) and then predict which side of the reaction is favored under equilibrium conditions.
For each reaction below, draw the mechanism (curved arrows) and then predict which side of the reaction is favored under equilibrium conditions.
For each reaction below, draw the mechanism (curved arrows) and then predict which side of the reaction is favored under equilibrium conditions.
Write an equation, using the curved-arrow notation, for the acid–base reaction that will take place when each of the following are mixed. If no appreciable acid–base reaction takes place, because the equilibrium is unfavorable, you should so indicate. (a) Aqueous NaOH and CH3CH2CO2H
Write an equation, using the curved-arrow notation, for the acid–base reaction that will take place when each of the following are mixed. If no appreciable acid–base reaction takes place, because the equilibrium is unfavorable, you should so indicate. (b) Aqueous NaOH and C6H5SO3H
Write an equation, using the curved-arrow notation, for the acid–base reaction that will take place when each of the following are mixed. If no appreciable acid–base reaction takes place, because the equilibrium is unfavorable, you should so indicate. (c) CH3CH2ONa in ethyl alcohol and ethyne
Write an equation, using the curved-arrow notation, for the acid–base reaction that will take place when each of the following are mixed. If no appreciable acid–base reaction takes place, because the equilibrium is unfavorable, you should so indicate (d) CH3CH2Li in hexane and ethyne
Write an equation, using the curved-arrow notation, for the acid–base reaction that will take place when each of the following are mixed. If no appreciable acid–base reaction takes place, because the equilibrium is unfavorable, you should so indicate. (e) CH3CH2Li in hexane and ethyl alcohol
What reaction will take place if ethyl alcohol is added to a solution of HC≡C:-Na+ in liquid ammonia?
Examine the reaction below. Identify the Bronsted acid, Bronsted base, conjugate acid, and conjugate base. Would the reaction work in the direction of the arrow? Explain why or why not.
Write the products for the following acid-base reaction. a) These reactions will be in equilibrium, and the equilibrium can favor one side or the other or be balanced (i.e. nearly equal). Indicate which side of the reaction is favored in the equilibrium either by use of arrows ⇌ or writing on one side of the reaction, “favored”. b) Draw the curved arrows to show the flow of e - for each of the reaction.
Glycine is an amino acid that can be obtained from most proteins. In solution, glycine exists in equilibrium between two forms: (a) Consult Table 3.1 and state which form is favored at equilibrium  
Predict the direction of the following acid-base equilibriums.  Be sure to label all species and include all necessary pKa’s. 
Predict the direction of the following acid-base equilibriums.  Be sure to label all species and include all necessary pKa’s. 
Predict the equilibrium (include pKa values in boxes):
Would water be a suitable proton source to protonate the following compound?
Which one of the following reactions will be favorable?
Would the following reaction proceed efficiently as written?
For each reaction below, draw the mechanism (curved arrows) and then predict which side of the reaction is favored under equilibrium conditions.
When methyl alcohol is treated with NaH, the product is HC 3O-Na+  (and H2) and not Na+ -CH2OH (and H2). Explain why this is so.
Alcohols can act as either acids or bases, similar to water. In the box below draw the products of the following reaction. 
Is the following equilibrium favoring the reactants or products?