EXERCISE 1

PROPERTIES THAT DISTINGUISH ORGANIC FROM INORGANIC COMPOUNDS

Organic Compounds Inorganic Compound

Flammable yes no

Melting Point low high

Boiling Point low high

Solubility in water no (for most) yes

Solubility in non-polar liquids yes no

Type of bonding covalent ionic

Reactions occur between: molecules ions

Atoms per molecule many few

Structure complex simple

Electrolyte no yes

Organic compounds are unstable. They are combustible, with many having no sharp melting points, decomposing, and charring at moderately high temperature.

Most are non-electrolytes. Most organic compounds contain the same kind and number of atoms but they exhibit

different sets of properties. Organic chemical reactions are relatively slow.

Name of Test Test Compound ResultIgnition Testsa. Flammability Ethyl alcohol Flammable

Water Non-flammableb. Charring Sucrose Positive

C12H22O11 + O2 + heat → CO2↑ + 11H2O↑ + 11C↓

Sodium chloride NegativeCalcium carbonate Negative

Name of Test Test Compound Observation Type of BondSolubility Tests Naphthalene in water Insoluble

Naphthalene in ether Soluble Covalent bondUrea in water Partially soluble H-bondingUrea in ether Soluble Covalent bond

Sodium chloride in water Soluble Ionic bondSodium chloride in ether Insoluble

Name of Test Test Compound ObservationElectrical Conductivity 1M sucrose Non-electrolyte

1M sodium chloride Electrolyte95% ethyl alcohol Non-electrolyte

n-hexane Non-electrolyte

EXERCISE 2

QUALITATIVE TESTS FOR ELEMENTS IN ORGANIC COMPOUNDS

Carbon and hydrogen are the predominant elements found in organic compounds. Next common elements are: oxygen, nitrogen, sulfur, phosphorus, halogens – chlorine,

bromine, and iodine. Least common elements include: arsenic, antimony, mercury, and other metals.

A. Test for Carbon and Hydrogen

Test compound: Glucose (C6H12O6)

Carbon and hydrogen are detected qualitatively by heating a mixture of the given substance with dry copper (II) oxide in a glass tube.

C6H12O6 + CuO → CO2↑ + H2O CO2 + Ca(OH)2 → CaCO3↓ + H2O

Glucose + CuO

heat

CO2 water vapor

gets trapped in lime water

Calcium carbonate Water

The presence of carbon is indicated by the formation of white precipitate. The presence of hydrogen is indicated by the formation of droplets of water in the cool

end of the tube. Copper (II) oxide acts as a catalyst.

B. Test for Nitrogen

Name of test: Soda-Lime Test Test compound: Urea

Soda-lime: NaOH-CaO (2:1 solid mixture) Nitrogen is usually detected by the formation of Prussian blue after the sodium fusion.

CO(NH2)2 + heat → NH3↑ + CO2

CO2 + Ca(OH)2 → CaCO3↓ + H2O

When heated with soda lime, urea decomposes and the nitrogen in the form of amino nitrogen (-NH2) will liberate ammonia gas.

Red litmus paper changes to blue.

C. Test for Halogen

Name of test: Beilstein Test Test compound: Chloroform (CHCl3)

An organic halogen compound imparts a green color flame when burned upon the surface of a copper wire.

The copper oxide formed from the copper wire reacts with the halogens to form the cuprous halide, which burns with a green flame.

Chlorine is the compound responsible for turning the flame green.

Name of test: Silver Nitrate Test Test compound: Monochloroacetic acid

Formation of insoluble silver halide upon treatment with silver nitrate in the presence of dilute nitric acid.

Nitric acid is necessary to remove cyanide and sulfide ions, otherwise, they form precipitates – silver cyanide is white and silver sulfide is black – that interfere with the detection of halogens.

Silver chloride – white precipitate.

D. Test for Oxygen

Name of test: Ferrox Test Test compounds: Acetone, ethyl alcohol, gasoline, benzene

Ferrox paper is prepared by soaking filter paper in methanol containing equal amounts of ferric chloride and ammonium thiocynate.

In the presence of oxygen, a deep red color is distributed between the filter paper and the test compound.

The test showed positive results for acetone and ethyl alcohol.

E. Test for Sulfur

Name of test: Lead Acetate Test Test compounds: Albumin

The presence of sulfur is detected by the production of brownish-black lead sulfide when albumin is treated with lead acetate in the presence of acetic acid.

Acetic acid prevents the formation of other insoluble lead salts. The production of brownish-black precipitate is due the presence of cysteine – the

amino acid part of albumin.

EXERCISE 3

Separation and Purification of Organic Compounds

QUALITATIVE TESTS FOR ELEMENTS IN ORGANIC COMPOUNDS

Recrystallization is a highly effective method for the purification of organic substances that exists already as crystals.

Processes Involved in Recrystallization1. Dissolving the material to form a saturated solution in a suitable solvent at an

elevated temperature.

Properties of a Desirable Solventa. Dissolves the solute easily at an elevated temperature, but only sparingly

at a lower temperature.b. Gives no chemical reaction with the solute.c. Sufficiently volatile so that it may be removed easily from the purified

crystals.

2. Filtering while hot to remove any suspended insoluble particles.3. Letting crystallization process

Stages of Recrystallization1. Removal of impurities, which may retard or inhibit crystal formation.

Samples that contain colored impurities maybe treated with decolorizing carbon to give rise to colorless solution.

Impurities are adsorbed by the active surface of the decolorizing carbon.

Animal charcoal is less effective at high than at low temperature.

The reason for operating at high temperature is to keep the substances from being crystallized in solution.

2. Nucleus formation Spontaneous nucleus formation is caused by the orientation and aggregation

of sufficient number of molecules, which may give rise to a crystal nucleus.

Methods of Inducing Crystal Formation1. Seeding – the process of adding a small crystal of pure material to induce

the crystallization process.2. Scratching the sides or bottom of a container with a glass rod – provides

sharp edges upon which crystal growth may occur.

3. Encouragement of growth of crystals to visible form. Growth of crystals maybe encouraged by stirring or agitation, which results in

distribution of the nuclei throughout the solution. Crystal growth in supersaturated solutions may be inhibited as

a result of restricted motion of the molecules.

A. Recrystallization of Benzoic Acid

Benzoic acid + NaCl + Methylene blue

heat

+ activated charcoal

filter

activated charcoal + methylene blue colorless solution

rapid cooling slow cooling

water coarse crystals water fine crystals

wash with cold distilled water

Benzoic acid crystals Benzoic acid crystals + +

hot distilled water hot distilled water + + HNO3 HNO3

+ +AgNO3 AgNO3

Colorless solution Colorless solution with crystals with crystals

Cloudy solution: NaCl + AgNO3 → NaNO3 + AgCl

B. Decolorization of Brown Sugar

Brown sugar + water

Brown sugar solution Brown sugar solution

Heat

+ Activated carbon

filter

activated charcoal + brown pigment Colorless solution

EXERCISE 4

Separation and Purification of Organic Compounds

SUBLIMATION

Sublimation – the direct conversion of a substance from solid to gas without passing through the liquid state.

o It can be applied when the components of a solid mixture differ appreciably in their vapor pressures.

o As a separation process, it involves gentle heating of the mixture in a confined container until the component with high vapor pressure changes into vapor phase, while the component with the lower vapor pressure is left in the container.

o As a purification process, it also depends on the difference of volatility. Less volatile or non-volatile impurities remain as residue while the sublimate is being formed.

Sublimate – the crystals, deposit, or material obtained when a substance is sublimated. o High vapor pressureo Low melting pointo More volatile

Residue – the solid particles that remained on the dish.o Low vapor pressureo High melting pointo Less or non-volatile

Deposition – the process of changing gas to solid without passing through liquid state.

SUBLIMATE RESIDUESalicylic acid – sodium sulfate mixture Salicylic Acid Sodium sulfate

Physical Appearance Needle-like Powder-likePolarity Non-polar PolarType of Compound Organic Inorganic

Observation Colorless solution with salicylic acid crystals

Cloudy solution with white precipitate

Salicylic acid + BaCl → no reactiono Salicylic acid is an organic compound, while barium chloride is an inorganic

compound. Na2SO4 + BaCl → NaCl + BaSO4↓

o Sodium sulfate is a polar inorganic compound that results to white precipitate (barium sulfate) when added with barium chloride.

EXERCISE 5

Separation and Purification of Organic Compounds

DISTILLATION

Distillation is usually employed for the purification of liquid organic substances. It involves evaporation and condensation.

o Evaporation – the conversion of liquid to vapor state with the aid of heato Condensation – the process in which vapor turns to liquid by cooling.

Distillate – the liquid that passed through the distilling flask. It requires a distillation flask fitted with a thermometer and a water-cooled condenser. Boiling chips are also used to prevent bumping by producing a constant steam of bubbles

which keeps the liquid in motion.

Boiling point is one of the most important criteria of purity, as it is constant in every pure organic substance at a definite pressure.

Distillation could be used to convert muddy water to potable water. o Solid particles should be allowed to settle and then decanted. Then, the water

should be heated to boil in low to moderate fire. It should be below the boiling point of water. This would rid the water of impurities.

The use of distillation is limited to a certain extent because some organic compounds decompose when an attempt is made to distill them at normal atmospheric pressure.

Common Types of Distillation1. Simple Distillation – used to separate a volatile liquid from a non-volatile solute.

– a large temperature difference (more than 20°) between the boiling points of the component is necessary to obtain efficient separation.

– the component which is more volatile will distill over first, in almost pure form at a definite constant temperature, the second component will distill over when the boiling point again remains constant for a long period of time.

2. Fractional Distillation – the process of collecting separate fractions according to arbitrary boiling point ranges during the distillation of a mixture of substances.

– It is performed readily by means of a special fractioning column.– It cannot be used if the components of a mixture have boiling points

very close together because some substances form a “constant boiling mixture”, also known as azeotropic mixture.

Azeotropic mixture – a mixture of liquids of certain definite composition that distills at constant temperature without change in composition.

4. Diminished-Pressure Distillation

.

5. Steam Distillation

Thermometer Reading Volume of Distillate Ignition Test Sodium-Nitroprusside Test

56°C 5 mL Flammable Red-wine colored

100°C 5 mL Slightly flammable Lighter color

Sodium-Nitroprusside Test – Clinical test for urine. Test for acetone.

EXERCISE 6

Separation and Purification of Organic Compounds

EXTRACTION OF CHLOROPHYLL

Extraction, by the use of solvents, is a frequently used method of withdrawing or substance from a mixture.

o It is usually performed using two immiscible solvents. The mixture is first dissolved in one of the liquids and then shaken with the other to distribute the components.

Aside from extraction, it also involves decantation and filtration.o Decantation – the process of separating solid-liquid components of mixtures by

gently pouring out the liquid so as not to disturb the solids that readily settle at the bottom of the container.

o Filtration – the process of separating the solid from the liquid by using a porous filter.

Residue – the solid particles that remained on the filtering medium. Filtrate – the liquid that passed through the filtering medium.

Water is usually one of the solvents used in the extraction process. The other liquid is usually a non-polar organic liquid.

o Diethyl ether – used extensively as an extracting solvent.– organic solvent– high solvent power for hydrocarbons and for oxygen-

containing compounds.– Highly volatile. It boils at 34.60°C – Fire hazard

o Ether – slightly soluble in water– Its efficiency can be improved by the addition of a small

amount of ionizable salt, such as NaCl.– The increase polar property of the water solution will cause a

decrease in the solubility of the organic solute. Salting-out effect – the reduced solubility in water in

the presence of an electrolyte.o Petroleum ether o Ligroin o Benzene o Carbon tetrachloride o Chloroform o Methylene chloride o Ethylene dichloride o N-butanol – slightly soluble in water

Extraction of water-immiscible solvent is useful for isolation of natural products that occur in animal and plant tissues that have high water content.

Extraction

Malunggay + sand

grind

+ hexane + methanol

decant

filter

crushed leaves and sand green solution

separatory funnel

dark green extract water-methanol solution +

anhydrous sodium sulfate

Chlorophyll

It acts as an agitator

Has polar and non-polar endWater solubleAbsorbs water It also absorbs other non-polar substances of malunggay

Non-polarExtracts chlorophyll of malunggay

Non-polar

Absorbs traces of water

EXERCISE 7

Separation and Purification of Organic Compounds

CHROMATOGRAPHY

Chromatography - the process of separating the substances in a complex mixture by their different affinities to the adsorbent.

It is one of the most useful methods of separating the components of minute amount of mixtures.

It used for analyzing mixtures of colored chemicals. It was invented by a Russian botanist, Mikhail Semyonovich Tsvet, in 1901, while

researching on plant pigments. This technique involves separation of constituent elements of the mixture. Chromatography is derived from the Greek words, chroma meaning color, and graphein

meaning to write. Thus, the word chromatography literally means color writing.

It has two phases: o Stationary Phase – refers to the column packing material and is either solid or

liquid. - It is usually a piece of high quality filter paper.

o Mobile Phase – represents a mobile phase of liquid or gas. - The mobile phase is a developing solution that travels up the stationary phase, carrying the samples with it.

Components of the sample will separate readily according to how strongly they adsorb on the stationary phase versus how readily they dissolve in the mobile phase.

Different Classification of Chromatographic Methods

1. Adsorption Chromatography (liquid-solid chromatography) – utilizes a mobile liquid or gaseous phase that is adsorbed onto the surface of a stationary solid phase. The equilibration between the mobile and stationary phase accounts for the separation of different solutes.

2. Partition Chromatography (liquid-liquid chromatography) – uses a thin film formed on the surface of a solid support by a liquid stationary phase. Solute equilibrates between the mobile phase and the stationary liquid.

3. Ion Exchange Chromatography – resin (the stationary solid phase) is used to covalently attach anions or cations onto it. Solute ions of the opposite charge in the mobile liquid phase are attracted to the resin by electrostatic forces.

4. Molecular Exclusion Chromatography (gel permeation chromatography) – liquid or gaseous phase passes through a porous gel which separates the molecules according to its size. The pores are normally small and exclude the larger solute molecules, but allow smaller

molecules to enter the gel, causing them to flow through a larger volume. This causes the larger molecules to pass through the column at a faster rate than the smaller ones.

Thin Layer Chromatography – it is usually used as an analytical technique rather than a preparative method.

o The stationary phase used is an adsorbent in the form of a thin layer of an inert solid on a supporting material, usually a think sheet of metal or plastic.

o The mobile phase is the solvent system used to separate the components of the mixture. Hexane and/or ethyl acetate is commonly used.

Paper Chromatography –a method used for testing the purity of compounds and identifying substances.

Technique:1. Introduce a small spot of the sample on the filter paper.2. Put the filter paper into a container that has the mobile phase. Make sure the plate

touches the mobile phase. 3. The solvent moves up the plate due to capillary action and carries the sample upwards.4. Remove the filter paper and allow it to dry5. Spray it with ninhydrin to make the spots more visible.

Ruhemann’s Purple - a purple coloration produced by ninhydrin in the presence of an amino acid.

Calculation of Retention Factor (Rƒ) Rƒ = distance traveled by the substance_

distance traveled by the solvent

Distance traveled by the solvent = 5.2 cmDistance traveled by the substance = 3.5 cm

5.2 cm

3.5 cm

Solvent front