Chapter 5
Classification of Organic Compounds by Solubility

1. 1. N – alcohols, aldehydes, ketones, esters with one functional group and more than five but fewer than nine carbons, ethers, epoxides, alkenes, alkynes, some aromatic compounds (especially those with activating groups).
   2. S1 – monofunctional alcohols, aldehydes, ketones, esters, nitriles, and amides with five carbons or fewer.
   3. A2 – weak organic acids; phenols, enols, oximes, imides, sulfonamides, thiophenols, all with more than five carbons; β‐diketones; nitro compounds with α‐hydrogens.
2. 1. Insoluble in water, soluble in 5% sodium hydroxide solution, soluble in 5% sodium bicarbonate solution.
   2. Soluble in water and ether, litmus paper turned blue.
   3. Insoluble in water, 5% sodium hydroxide solution, and 5% hydrochloric acid solution, but soluble in 96% sulfuric acid solution.
   4. Soluble in water and ether; litmus paper is unchanged in color.
   5. Soluble in water and ether; litmus paper is unchanged in color.
   6. Insoluble in water and 5% sodium bicarbonate solution, but soluble in 5% sodium hydroxide solution.
3. 1. A1
   2. SB
   3. N
   4. S1
   5. S1
   6. A2
4. Both acyl halides and anhydrides react with water, so any results would be of the carboxylic acid that is formed from the hydrolysis of these compounds.
5. 1. 1‐Propanol is more soluble in water than diethyl ether. 1‐Propanol can hydrogen bond with water, whereas diethyl ether does not hydrogen bond with water.
   2. Pentanedioic acid is more soluble in water than butanedioic acid. Odd carbon number of dioic acids have less intracrystalline forces than even carbon number of dioic acids.
   3. Methyl methacrylate is more soluble in water than poly(methyl methacrylate). Polymers are insoluble in water.
   4. Butanoic acid is more soluble in water than 2‐Bromobutanoic acid. The addition of halogens increases the molecular weight and decreases the solubility.
   5. 2‐Methylpropanoic acid is more soluble in water than butanoic acid. Branching lowers the boiling point and lowers intermolecular forces. Thus, a branched compound is more soluble in water than a straight chain molecule.
6. 1. 1‐Chlorobutane is insoluble in water since it is an haloalkane. It is insoluble in 5% sodium hydroxide solution, 5% hydrochloric acid solution, and 96% sulfuric acid solution. Thus 1‐Chlorobutane is in solubility class I.
   2. 4‐Methylaniline is insoluble in water since it is an aniline. It is basic, due to the presence of the amino group, and therefore is insoluble in 5% sodium hydroxide solution, but soluble in 5% hydrochloric acid solution, and thus 4‐methylaniline is in solubility class B.
   3. 1‐Nitroethane is insoluble in water since it is a weak organic acid. It is soluble in 5% sodium hydroxide solution, but insoluble in 5% sodium bicarbonate solution, and thus 1‐nitroethane is in solubility class A2.
   4. Alanine is an amino acid, thus is amphoteric, and soluble in water. Alanine is insoluble in ether and thus in solubility class S2.
   5. Benzophenone is insoluble in water because it has more than five carbon atoms. Since it is a neutral compound, containing only carbon, hydrogen, and oxygen, it is insoluble in water, 5% sodium hydroxide solution, and 5% hydrochloric acid solution. It is soluble in 96% sulfuric acid solution. Therefore, benzophenone is in solubility class N.
   6. As a strong organic acid, benzoic acid is insoluble in water, soluble in 5% sodium hydroxide solution, and soluble in 5% sodium bicarbonate solution. Therefore, benzoic acid is in solubility class A1.
   7. As a saturated hydrocarbon, hexane is insoluble in water, 5% sodium hydroxide solution, 5% hydrochloric acid solution, and 95% sulfuric acid. Hexane is in solubility class I.
   8. 4‐Methylbenzyl alcohol is insoluble in water since it has more than five carbon atoms. It is a neutral compound with only carbon, hydrogen, and oxygen. It is insoluble in water, 5% sodium hydroxide solution and 5% hydrochloric acid solution. However, 4‐methylbenzyl alcohol is soluble in 96% sulfuric acid and thus in solubility class N.
   9. As an amine with less than six carbons, ethylmethylamine is soluble in water. It is soluble in ether and its aqueous solutions turn litmus paper blue, therefore it is basic. Ethylmethylamine is in solubility class SB.
   10. Propoxybenzene is insoluble in water because it has more than five carbon atoms. It is a neutral compound with only carbon, hydrogen, and oxygen and is insoluble in 5% sodium hydroxide solution, and 5% hydrochloric acid solution. However, propoxybenzene is soluble in 96% sulfuric acid solution and in solubility class N.
   11. Propanal is soluble in water because it has less than five carbons. As a neutral compound, it is soluble in ether and its aqueous solutions do not change the color of litmus paper. Propanal is in solubility class S1.
   12. As an aryl halide, 1,3‐Dibromobenzene is insoluble in water, 5% sodium hydroxide solution, 5% hydrochloric acid solution, and 96% sulfuric acid. 1,3‐Dibromobenzene is in solubility class I.
   13. Propanoic acid is soluble in water because it contains less than five carbon atoms. It is soluble in ether, but its aqueous solutions turn litmus paper red. Propanoic acid is in solubility class SA.
   14. As a weak organic acid, benzenesulfonamide is insoluble in water. It is soluble in 5% sodium hydroxide solution but insoluble in 5% sodium bicarbonate solution. Benzenesulfonamide is in solubility class A2.
   15. 1‐Butanol is soluble in water because it contains less than five carbon atoms. It is soluble in ether and its aqueous solutions do not change the color of litmus. 1‐Butanol is in solubility class S1.
   16. Methyl propanoate is soluble in water since it contains less than five carbon atoms. It is soluble in ether and its aqueous solutions do not change the color of litmus. Methyl propanoate is in solubility class S1.
   17. 4‐Methylcyclohexanone is insoluble in water since it contains more than five carbon atoms. It is also insoluble in 5% sodium hydroxide solution and 5% hydrochloric acid solution, but soluble in 96% sulfuric acid. Therefore, 4‐methylcyclohexanone is in solubility class N.
   18. Since 4‐Aminobiphenyl is an aniline, it is insoluble in water. It is insoluble in 5% sodium hydroxide solution, but soluble in 5% hydrochloric acid solution. 4‐Aminobiphenyl is in solubility class B.
   19. Since 4‐Methylacetophenone contains more than five carbon atoms, it is insoluble in water. It is also insoluble in 5% sodium hydroxide solution and 5% hydrochloric acid solution, but soluble in 96% sulfuric acid. Therefore, 4‐methylacetophenone is in solubility class N.
   20. Naphthalene is insoluble in water since it contains more than five carbon atoms. It is insoluble in 5% sodium hydroxide solution and 5% hydrochloric acid solution. However, naphthalene is soluble in 96% sulfuric acid, and therefore in solubility class N.
   21. Phenylalanine is an amino acid, thus is amphoteric, and soluble in water. Phenylalanine is insoluble in ether and thus in solubility class S2.
   22. Benzoin is insoluble in water since it has more than five carbon atoms. It is insoluble in water, 5% sodium hydroxide solution, and 5% hydrochloric acid solution. However, benzoin is soluble in 96% sulfuric acid, and therefore in solubility class N.
   23. As a strong organic acid, 4‐hydroxybenzenesulfonic acid is insoluble in water. However, it is soluble in 5% sodium hydroxide solution and 5% sodium bicarbonate solution. 4‐Hydroxybenzenesulfonic acid is in solubility class A1.
7. Listed in order from least basic to most basic (see next question).

8. Benzanilide

   Solubility class

   N

   Pentylamine

   Solubility class

   SB

   Diphenylamine

   Solubility class

   N

   Benzylamine

   Solubility class

   SB

   4‐Methylaniline

   Solubility class

   B

   Butanamide

   Solubility class

   S1

9. Listed in order from least soluble to most soluble in water.
   1. Smaller alcohols are more soluble.
   2. More hydroxyl groups increase solubility.
   3. Branching increases solubility.
   4. N < S1–N < SB < S2

10. 1. Methanol

       Solubility class

       S1

       Isopropyl alcohol

       Solubility class

       S1

       Ethanol

       Solubility class

       S1

       1‐Butanol

       Solubility class

       S1

    2. Butane

       Solubility class

       I

       1,4‐Butanediol

       Solubility class

       S2

       1‐Butanol

       Solubility class

       S1

    3. ...

       1‐Butanol

       Solubility class

       S1