Chem31.1 Experiment 7 Slides

Cala, Jean Kathleen B.

Vera Cruz, Aika Gail J.

*

*

*Solubility of organic compounds is a

property that provides information

regarding the identity and the

structure of the substance such as its

functional groups and what elements

it contains. Solubility depends on

various factors such as the nature of

the solute, temperature, and

pressure.

*In general, the tendency of a solute

to dissolve in a solvent basically

depends on the ability of the solute

to interact effectively enough with

the solvent molecules.

*The dissolving process involves

breaking of attractive forces among

solute and solvent particles, but the

breaking of the forces between the

solute particles and the solvent

particles is also observed.

*Polarity is one great factor for it

determines what reacts with what as

indicated in the “Like dissolves like”

principle.

*A polar solute dissolves in a polar solvent

because they interact with each other

through dipole-dipole.

*Nonpolar solutes and nonpolar solvents

interact with each other through London

dispersion forces (LDF). The presence of an

acidic CO2H or basic NH2 group in a water-

soluble compound can be detected by low

or high pH, respectively, of the solution.

*

*In the experiment, the solubilities

of 14 different organic compounds

were evaluated by testing it to

different solvent systems.

Different procedures were

conducted to solid and liquid

samples.

*

*About 30mg of each sample were obtained

in different test tubes. For every test

tube, 20 drops of the different solvent

systems were added. This was repeated

seven times for there are 7 solvent

systems to be tested. Each sample was

classified as completely soluble = +++,

partially soluble = ++, slightly soluble = +,

and insoluble = X, depending on its

reaction to the solvent.

*

Benzoic Acid

Sulfanilic Acid

Alanine

Phenol

OH

Salicylic Acid

*

*2 drops of each sample was obtained

in different test tubes. 20 drops of

the solvent was then added to the

test tube, as well. This was procedure

was repeated for each solvent. The

dissolution of the sample was

determined and classified as

completely miscible = +++, partially

miscible = ++, and immiscible = X.

*

Acetic Acid

Hexane

Benzamide

Aniline

Chlorobenzene

Ethylamine

Ethylacetate

Benzene

Cyclohexane

E-naphthol

*

Sample Water 5% NaOH 5% HCl 5%NaHCO3 Ether Conc.

H2SO4

85%

H2PO4

Alanine ++ +++ ++ ++ X X +

Aniline X X +++ X +++ +++ ++

Benzamide X X X + +++ ++ +

Benzene X ++ +++ +++ X X X

Benzoic Acid X +++ ++ +++ +++ + ++

Chlorobenze

ne

X +++ ++ +++ X + ++

Cyclohexane X X X X +++ X ++

Ethylamine +++ X +++ X +++ X X

Ethylacetate +++ +++ X ++ +++ X ++

Hexane X X ++ ++ +++ X X

E-naphtol X ++ +++ ++ +++ ++ +

Phenol ++ +++ +++ X +++ +++ X

Salicylic Acid X ++ +++ +++ +++ ++ +

Sulfanilic

Acid

+ +++ +++ +++ + ++ ++

*

Sample Water 5% NaOH 5% HCl 5%NaHCO3 Ether Conc.

H2SO4

85%

H2PO4

Alanine ++ +++ ++ ++ X X +

Aniline X X +++ X +++ +++ ++

Benzamide X X X + +++ ++ +

Benzene X ++ X +++ X X X

Benzoic Acid X +++ X +++ +++ + ++

Chlorobenze

ne

X +++ X +++ X + ++

Cyclohexane X X X X +++ X X

Ethylamine +++ X +++ X +++ X X

Ethylacetate +++ +++ X ++ +++ X ++

Hexane X X X X +++ X X

E-naphtol X ++ +++ ++ +++ ++ +

Phenol X +++ +++ X +++ +++ X

Salicylic Acid X ++ +++ +++ X ++ +

Sulfanilic

Acid

+ +++ +++ +++ X ++ ++

*

*

*In considering solubility in water a

substance is arbitrarily said to be

“soluble” if it dissolves to the extent

of 3g per 100mL of solvent.

*Water is a poor solvent for

hydrocarbons. The introduction of

halogen atoms does not alter the

polarity appreciably. Organic salts, on

the other hand, are water soluble.

*Acids and amines are generally more

soluble than neutral compounds.

*Branching of the alkyl chain of the

molecule lowers intermolecular forces

between its molecules, causing greater

solubility in water. This occurs simply

because the molecules of the branched

compound are more easily separated from

one another.

*Compounds with four or less carbons, and

which contain polar groups of oxygen,

nitrogen or sulfur, will often be soluble in

water. Compounds with five or six carbons

with those elements will often have

borderline solubility or be insoluble.

*

*Acids are soluble in 5% NaOH, a strong base, but

only strong acids are soluble in 5% NaHCO3, a

weak base.

*Strong acids: Carboxylic acids, sulfonic acids,

sulfinic acids, phenols with e-withdrawing

groups in the ortho- and/or para- positions

*Weak acids: phenols, some enols, imides,

primary and secondary nitro compounds,

arylsulfonyl derivatives of primary amines,

unsubstituted arylsulfonamides, oximes,

thiophenols

*Aldehydes and ketones are far too weakly acidic

to dissolve to any measurable extent in NaOH

solution.

*

*Aliphatic amines, primary, secondary, and

tertiary, form salts with hydrochloric acid.

Hence, they are soluble in dilute HCl.

*Aryl groups diminish the basicity of the

amine. Primary aromatic amines, although

more weakly basic than primary aliphatic

amines, are soluble in dilute HCl.

Diarylamines and triarylamines are not

soluble.

*Disubstituted amides (RCONR’2) which are of

sufficiently high molecular weight to be

water insoluble are soluble in dilute HCl.

*

*Ether is a slightly polar molecule.

*A compound that dissolves in both

water and ether means that it has both

a considerable nonpolar and polar

characteristics.

*Polyfunctional compounds and

derivatives as well as salts are too polar

to dissolve in ether while monofuctional

compounds are soluble in ether.

*

*Conc. H2SO4 is used with neutral, water-

insoluble compounds containing no elements

other than carbon, hydrogen, and oxygen.

*If the compound is unsaturated, is readily

sulfonated, or possesses a functional group

containing oxygen, it will dissolve in

concentrated H2SO4.

*Alkanes, cycloalkanes, and their halogen

derivatives are insoluble in concentrated

H2SO4.

*Simple aromatic hydrocarbons, and their

halogen derivatives do not undergo sulfonation

and are insoluble in concentrated H2SO4.

However, the presence of two or more alkyl

groups on the aromatic ring permits the

compound to be sulfonated.

*Phosphoric acid is not nearly as strongly acidic

as is sulfuric acid. It is capable of dissolving

most of the oxygen containing compounds such

as alcohols, aldehydes, and esters, but is not

able to dissolve unsaturated hydrocarbons such

as alkenes, alkynes or aromatics.

*

*The solubility or miscibility of a

solute to a solvent is generally

dependent on its nature. The

solubility classification of an

organic compound is based on its

composition, structure,

properties and presence of

functional groups.

*

*Construct a schematic diagram

for the determination of the

solubility characteristics of

organic compounds.

Wate

r

Soluble Ether

Insoluble Salts of organic acids, amine hydrochlorides, amino acids, polyfunctional compounds with hydrophilic functional groups: carbohydrates (sugars), polyhydroxy compounds,

polybasic acids, etc.

Soluble

Acidic – Monofunctional carboxylic acids with five carbons or fewer; arylsulfonic acids

Basic – Monofunctional amines with six carbons or fewer

Neutral – Monofunctional alcohols, aldehydes, ketones, esters, nitriles, and amides with five carbons or fewer

Insoluble 5% NaOH

Soluble 5%

NaHCO3

Soluble Strong organic acids: Carboxylic acids with more than six carbons; phenols with electron-widthrawing groups in the ortho and/or para

position(s); β – diketones (1,3 – diketones)

Insoluble Weak organic acids: phenols, enols, oximes, imides,

sulfonamides, thiophenols, all with more than five carbons; β – diketones; nitro compounds with α - hydrogens

Insoluble 5% HCl

Soluble Aliphatic amines with eight or more carbons; anilines (only one phenyl group attached to nitrogen); some

ethers

Borderline Miscellaneous neutral compounds containing nitrogen

or sulfur and having more than five carbon atoms

Insoluble Conc. H2SO4

Soluble 85% H3PO4

Soluble Alcohols, aldehydes, ketones, esters with one functional group and more than 5 but fewer than 9 carbons, ethers, epoxides

Insoluble Alkenes, alkynes, some aromatic

compounds

Insoluble Saturated hydrocarbons, haloalkenes, aryl

halides, other deactivated aromatic compounds, diaryl ethers

*

* Castro, A. (2009). Solubility of organic compounds. Unpublished manuscript,

Physical Sciences Department, De La Salle University - Dasmariñas,

Dasmariñas, Cavite.

* Classification of organic compounds by solubility. (2004, October 28).

Retrieved from

http://opencourseware.kfupm.edu.sa/colleges/cs/chem/chem303/files\3-

Lecture_Notes_CHEM-303_(Chapter_5).pdf

* Kelly, B. (1997, December 31). Organic qualitative analysis. Retrieved from

http://faculty.swosu.edu/william.kelly/pdf/qo3.pdf

* Shriner, R. L., Fuson, R. C., & Curtin, D. Y. (1965). The systematic

identification of organic compounds (5th ed.). New York: Wiley.

* Trainor, D., Huang, A., & Moyer, J. (2012). Procedure for determining

solubility of organic compounds. Retrieved

from http://www.wellesley.edu/Chemistry/chem211lab/Orgo_Lab_Manual/Ap

pendix/ClassificationTests/solubility.html