Fundamental Organic Chemistry (I)

231

(Lab Manual)

Edited By:

Nada Tashkandi

Under supervision of:

Dr. Hamida Abdel Hamid

1428-1429H

Safety Precautions

1-Safely Using Chemicals

When working with volatile materials, remember that heat causes expansion, and confinement of expansion results in explosion. Remember also that danger exists even though external heat is not applied.

Do not mix sulfuric acid with water inside a cylinder. The heat from the reaction can break the base of the vessel because of the thickness of the base and the seal.

Perchloric acid is especially dangerous because it explodes on contact with organic materials.

Glass will be chemically attacked by hydrofluoric acid, hot phosphoric acid and strong hot alkalis, so it should never be used to contain or to process these materials.

Always flush the outside of acid bottles with water before opening. Do not put the stopper on the counter top where someone else may come in contact with acid residue.

Mercury is highly toxic. Special care is needed when dealing with mercury.

2-Identifying chemicals - DO NOT taste chemicals for identification. Smell chemicals only when necessary and only by wafting a small amount of vapor toward the nose.

3-Label with care - Never fill a receptacle with material other than that specified by the label. Label all containers before filling.

4-Safely Handling Glassware

Handle glassware carefully. Hold beakers, bottles and flasks by the sides and bottoms rather than by the tops. The rims of beakers or necks of bottles and flasks may break if used as lifting points. Be especially careful with multiple neck flasks.

5-Avoid Over Tightening Clamps - To avoid breakage while clamping glassware, use coated clamps to prevent glass-to-metal contact, and do not use excessive force to tighten clamps.

6-Safely Using Heat Sources

Be sure to check laboratory or instruction manuals when working with heat sources.

7-Bunsen Burners
Adjust Bunsen Burner to get a large soft flame. It will heat slowly but also more uniformly. Uniform heat is a critical factor for some chemical reactions.

Adjust the ring or clamp holding the glassware so that the flame touches the glass below the liquid level. Heating above the liquid level does nothing to promote even heating of the solution and could cause thermal shock and breakage of the vessel. A ceramic-centered wire gauze on the ring will diffuse the burner flame to provide more even heat.

Rotate test tubes to avoid overheating one particular area. Uniform heating may be critical to your experiment. Heat all liquids slowly. Fast heating may cause bumping, which in turn may cause the solution to splatter. Do not heat glassware directly on electrical heating elements. Excessive stress will be induced in the glass, and this can result in breakage.

8-Hot Plates
Always use a hot plate larger than the vessel being heated. Thick-walled items such as jars, bottles, cylinders and filter flasks should never be heated on hot plates.

9-Evaporation
Evaporation work should be observed carefully. Be careful when handling a vessel that has been heated after evaporation has occurred. It may crack unexpectedly.

10-Heating Thick-Walled Vessels
Glassware with thick walls such as bottles and jars should not be heated over a direct flame or comparable heat source.

11-Scratched Glassware
Do not heat glassware that is etched, cracked, nicked or scratched. It is more prone to break.

12-Mixing and Stirring
Use a rubber policeman on glass, or use Teflon rods to prevent scratching the inside of a vessel. Do not look down into any vessel being heated or containing chemicals. Do not point a vessel’s open end at another person. A reaction may cause the contents to be ejected. Spattering from acids, caustic materials and strong oxidizing solutions on the skin or clothing should be washed off immediately with large quantities of water.

13-Pipetting

Do not pipet by mouth. For your safety, we suggest using a mechanical pipetting device. Do not draw any liquids into a pipet by mouth. Serious injury could result.

14-Vacuum and Pressure Warning

All glass containers used in vacuum work or which are under vacuum must be securely and adequately taped or shielded to restrain flying glass in the event of an implosion or other accident. Always wear safety glasses, goggles, or a face shield.

Because of variations in conditions, Corning cannot guarantee any glassware against breakage under vacuum or pressure. Adequate precautions should be taken to protect personnel doing such work.

15- Ventilation

Always work in a well-ventilated area. When working with chlorine, hydrogen sulfide, carbon monoxide, hydrogen cyanide and other very toxic substances, always use a protective mask or perform these experiments under a fume hood in a well-ventilated area. Cryogenic liquids should be stored and handled in well-ventilated areas to prevent excessive buildup of gas concentration. These should never be used in closed environmental chambers

Some glassware used in lab:

Some important techniques:

1-Crystallization

Crystallization is a technique which chemists use to purify solid compounds. Crystallization is based on the principles of solubility: compounds (solutes) tend to be more soluble in hot liquids (solvents) than they are in cold liquids. If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound. Impurities are excluded from the growing crystals and the pure solid crystals can be separated from the dissolved impurities by filtration.

How to do a crystallization

To crystallize an impure, solid compound, add just enough hot solvent is added to it to completely dissolve it. The flask then contains a hot solution, in which solute molecules – both the desired compound and impurities – move freely among the hot solvent molecules. As the solution cools, the solvent can no longer “hold” all of the solute molecules, and they begin to leave the solution and form solid crystals. During this cooling, each solute molecule in turn approaches a growing crystal and rests on the crystal surface. If the geometry of the molecule fits that of the crystal, it will be more likely to remain on the crystal than it is to go back into the solution. Therefore, each growing crystal consists of only one type of molecule, the solute. After the solution has come to room temperature, it is carefully set in an ice bath to complete the crystallization process. The chilled solution is then filtered to isolate the pure crystals and the crystals are rinsed with chilled solvent.

2-Filtration

Filtration is a technique used either to remove impurities from an organic solution or to isolate an organic solid. The two types of filtration commonly used in organic chemistry laboratories are gravity filtration and vacuum or suction filtration.

Gravity Filtration

Gravity filtration is the method of choice to remove solid impurities from an organic liquid. The "impurity" can be a drying agent or an undesired side product or leftover reactant. Gravity filtration can be used to collect solid product, although generally vacuum filtration is used for this purpose because it is faster.

A filtration procedure called "hot gravity filtration" is used to separate insoluble impurities from a hot solution. Hot filtrations require fluted filter paper and careful attention to the procedure to keep the apparatus warm but covered so that solvent does not evaporate.

Vacuum Filtration

Vacuum filtration is used primarily to collect a desired solid, for instance, the collection of crystals in a recrystallization procedure. Vacuum filtration uses either a Buchner or a Hirsch funnel.Vacuum filtration is faster than gravity filtration, because the solvent or solution and air is forced through the filter paper by the application of reduced pressure. The reduced pressure requires that they be carried out in special equipment:

·  Buchner or Hirsch funnel

·  heavy-walled, side arm filtering flask

·  rubber adaptor or stopper to seal the funnel to the flask when under vacuum

·  vacuum source

SATURATED AND UNSATURATED HYDROCARBONS

Cyclohexane

Result / Observation / Test
It is saturated compound.

1-Bromo cyclohexane / The colour of bromine is not discharged from the first tube.
The colour of the second tube disappears. / 1-Bromination
In two test tubes put 1ml of cyclohexane +3ml of bromine with will constant shaking.
Leave the first tube in light, expose the second to sun light for 15min.
It is saturated compound. / The violet colour of the Permanganate does not Change. / 2-Potasium Permanganate Test
In a test tube Put 1ml of cyclohexane+ few drops of dil acidic KMnO4 with shaking

Cyclohexene

Preparation of cyclohexene:

Procedure:

To 3ml of cyclohexanol in a dry test tube, add 0.5ml of Conc. H2SO4and perform the following experiments:

Result / Observation / Test
It is unsaturated compound. / The orange colour of bromine discharged immediately / 1-Bromination
To 1ml of cyclohexene in a test tube add drops of bromine
It is unsaturated compound. / The violet colour of the Permanganate disappears immediately. / 2-Potasium Permanganate Test
In a test tube Put 1ml of cyclohexane+ few drops from dil KMnO4 acidify with sulfuric acid.

Acetylene

H-CºC-H

Preparation of Acetylene:

Acetylene gas prepared by adding water to Calcium Carbide

CaC2

Procedure:

To 0.25gm of Calcium Carbide in a dry test tube add 1ml of water and the acetylene gas will appear, perform the following experiments on it:

Result / Observation / Test
It is unsaturated compound. / The orange colour of the bromine disappear immediately / 1-Bromination
Pass the acetylene gas on a test tube contains bromine.
It is unsaturated compound. / The colour of the Permanganate disappears immediately. / 2-Potasium Permanganate Test
Pass the acetylene gas on a test tube contains dil KMnO4 acidify by Conc. H2SO4.
HCºCAg
silver acetylide / White precipitate forms. / 3-Pass the acetylene gas on a test tube that contains Ammonical silver nitrate.

Aromatic Hydrocarbons

Benzene

Result / Observation / Test
/ Red-brown colour appears. / 1-Le Rosen test:
To 1 ml of benzene add 1ml of formaldehyde, and then add few drops of H2SO4.

Nitro benzene / Yellow oily layer will be separated / 2-Nitration
To 5ml of equal volume of HNO3 and Conc. H2SO4 add gradually 1ml of Benzene with shaking, cool the mixture for about 2 minutes, pour into cold water

Toluene

Result / Observation / Test

o-Nitro P-Nitro
toluene toluene / Yellow oily layer will be separated / 1-Nitration
To one ml of HNO3 in a test tube add 1ml of sulfuric acid then add gradually 0.5ml of Toluene with shaking then pour the content of the tube in beaker that contain ice.

Alcohols

Monohydric Alcohols

Methanol

CH3OH

Result / Observation / Test
Cr2(SO4 )3 / The orange colour of the solution changes to green. / 1-Oxidation
5ml of K2Cr2O7 solution + 2ml [CH3OH + dil. H2SO4 ] warm in water bath.

Methyl salicylate / Oil of winter green forms. / 2-Esterification 1ml of CH3OH + 0.5gm salicylic acid +Conc. H2SO4heat in water bath for 5 min.cool then pour the content of the test tube in a few ml of cold water in a basin.
-ve / 3-Iodoform test:
3ml of iodine solution+1ml of CH3OH + NaOH
Solution drop wise until the iodine colour just disappear
D
W.B.

Ethanol

Result / Observation / Test
Cr2(SO4 )3 / The orange colour of the solution changes to green. / 1-Oxidation
1ml of C2H5OH + K2Cr2O7 +2drops of dil H2SO4 then heat in water bath.
CH3COOC2H5
Ethyl Acetate / Fruity odor appears / 3-Esterification 1ml of C2H5OH +0.5 gm of Sodium acetate+ Conc. H2SO4heat in water bath for 5 min. then pour the content of the test tube in ice cold water.
CHI3
Iodoform / Yellow ppt. / 3- Iodoform test:

Dihydric Alcohols

Ethylene glycol

Result / Observation / Test
Pink colour / 1-Action of potassium hydrogen sulphate: Heat 1ml of ethylene glycol with 3gm potassium hydrogen sulphate on direct flame, then collect the acetaldehyde given in another test tube. Test for acetaldehyde by Schiff¢s reagent
Pink colour appears with heating and disappears with cooling. / 2-Borax test
To 1% of borax solution in a test tube, add drops of phenol phethalen (Ph.Ph.) then add drops of ethylene glycol, heat.

Trihydric Alcohols

Glycerol


Result / Observation / Test
CH2=CH.CHO
Acrolien / Characteristic and irritating odour produced. / 1- Acrolein test:
Heat 0.5ml of glycerol with 1gm of finely powdered potassium hydrogen sulphate D

Pink colour appears with heating and disappears with cooling. / 2-Borax test
To 1% of borax solution in a test tube, add drops of phenol phethalen (Ph.Ph.) then add drops of glycerol, D
W.B.

Aldehydes

Formaldehyde

Result / Observation / Test
Ag¯+HCOOH
Ag2O / A brilliant silver mirror is deposited on the inner walls of the test tube.
Black ppt. / 1-Reduction Reaction:
a-1ml of HCHO
+ few drops of ammoniacal AgNO3 ,
D
W.B..
If the tube heated directly.
Cu2O
Cupric oxide / Reddish brown ppt. / b- 1ml HCHO+2ml of Fhling¢s solution
[fehling A +fehling B]
D
W.B.
Pink colour / 2-Colour reaction of formaldehyde:
1ml HCHO+1ml of Schiff¢s reagent
-ve / 3- Iodoform test:

Acetaldehyde

Result / Observation / Test
Ag¯
Cu2O / Silver Mirror
Red ppt. / 1-(1ml)CH3CHO+
Ammoniacal AgNO3 D
W.B.
2-(1ml) CH3CHO+ Fehling¢s reagent D
W.B.
Acetaldehyde is an aldehyde. / Red colour forms. / 2- Schiffs reagent test:
1ml CH3CHO +1ml of Schiff¢s reagent
Red colour forms. / 4-Sodium nitroprusside test:
1ml of freshly prepared solution of sodium nitroprusside + CH3CHO solution +dil. NaOH solution in excess.
CHI3
Iodoform / Yellow crystals / 5- Iodoform test:

Chloral Hydrate