LAB

LAB 6   COMPARATIVE INVESTIGATION OF ORGANIC COMPOUNDS PRE-LAB 1. Differentiate the following types of functional groups a. Principal groups play a key role in the determination of structure and reactivity. Subordinate groups come into play once the confirmation for principal groups has been reached. 2. Enumerate the different interactive forces involved during a solution process Hydrogen Bonding - is the electrostatic attraction between polar molecules that occurs when a hydrogen (H) hydrogen (H) atom bound to a highly electronegative atom such as nitrogen (N), oxygen (O) or fluorine (F) experiences attraction to some other nearby highly electronegative atom. Dipole-Dipole - Dipole-Dipole interactions result when two dipolar molecules interact with each other through space. When this occurs, the partially negative portion of one of the polar molecules is attracted to the th e partially positive portion of the second polar molecule. This type of interaction between molecules accounts for many physically and biologically significant phenomena such as the elevated boiling point of water. London Dispersion Forces - (LDF, also known as dispersion forces, forces, London forces, forces, instantaneous dipole – induced induced dipole forces, forces, or loosely van der Waals forces) forces) are a type of force  force  acting between atoms and molecules. They are part of the van der Waals forces. forces. Vander Waals Forces - is the sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds,  bonds,  or the electrostatic interaction of  of  ions with one another, with neutral molecules, or with charged molecules. molecules.[1] The resulting van der Waals forces can be attractive or repulsive  – 

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As shown in the table, most of the hydrocarbons are clear. The result of the experiment showed that Phenol becomes red upon oxidation and white crystals for benzoic acid. The odors of the compounds are quite similar to each other but still have different identity. Cyclohexane and DCM both have paste-like odor. Ethanol smells like alcohol while benzoic acid is odorless. Ethyl acetate has plastic balloon odor while ethylamine has urine odor or can be ammoniacal odor because of its functional group, amine. B. Test for Solubility Properties of Sample in H2O, 5% NaOH solution and 5% HCl solution Table 2. Solubility of sample in different solvents

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A. Observation of Physical State at Room Temperature, Color and Odor of Samples Table 1. Intrinsic properties of samples

The solubility properties of organic compounds using H2O, 5% NaOH solution and 5% HCL solution indicates whether the solid sample is soluble or insoluble and if the liquid sample is miscible and immiscible. Solubility of sample to the solvent is related to polarity of the two substances and the intermolecular forces of attraction during the solution process. The “like dissolves like” principle is involved. Water   is a polar solvent so the sample that is soluble or miscible with water is also polar. Based on the results, ethanol, phenol, ethyl acetate and ethylamine are polar compounds. The solubility in 5% NaOH solution of a water insoluble sample is an indication that acidic functional group is present. Compounds that behave as bases in aqueous solution are detected by their solubility in 5% HCl solution. Ethanol and phenol are miscible while benzoic acid is very soluble in 5% NaOH solution. The rest of samples are immiscible. Ethanol and ethylamine are miscible in 5% HCl solution while the rest of the samples are immiscible and benzoic acid is insoluble. Reaction with litmus paper indicated acidity, basicity or neutrality of water-soluble samples. Acidic solution turns blue litmus paper to red and red litmus paper to red. Blue litmus paper to blue and red litmus paper to blue indicates a basic solution. Neutral solution is characterized by blue to blue litmus paper and red to red litmus paper.

2C2H2 + 5O2

 4CO2 + 2H2O + heat

→

Based on the table, cyclohexane, phenol, ethyl acetate and ethylamine are flammable with luminous flame while ethanol with nonluminous flame. DCM and benzoic acid are both non-flammable LAB 7   CLASSIFICATION HYDROCARBONS  – 

As shown in the table, phenol and ethyl acetate are acidic while ethylamine is basic. Ethanol is a neutral sample. Cyclohexane, DCM and benzoic acid were not subjected to the litmus paper test because of their immiscible property with water.

The result of the Ignition test indicates the presence of unsaturated or high carbon to hydrogen ratio. The degree of luminosity can be assessed by the presence of yellow or luminous flame. The aromatic compounds burn with sooty flame due to the incomplete combustion, which causes the formation of an unburned carbon. The higher the number of Carbon atoms, the higher the degree of luminosity. In addition, the higher the Carbon: Hydrogen Ratio, the higher the degree of luminosity. In terms of degree of luminosity: aromatic compound > unsaturated hydrocarbon > saturated hydrocarbon. Complete combustion is indicated by a blue flame (non-luminous) and there is more heat than light, the carbon is completely oxidized. 2C10H22 +31O2

 20CO2 +22H2O

→

Incomplete combustion is indicated by a yellow flame (luminous) and there is much light than heat; the carbon is not completely oxidized.

TESTS

FOR

Hexane alkane hydrocarbon with a chemical formula of C6H14, has a molar mass of 86.18 g/mol, and a boiling point of 69°C. Isomers of hexane are mostly non-reactive, and are frequently used as solvents in organic reactions because they are very non-polar. It is a very important constituent in gasoline and is also used in food processing.

1. Differentiate: a. Acyclic and cyclic Cyclic hydrocarbons are molecules that have carbon atoms that are combined to form one or more rings. Acyclic hydrocarbons are carbons that are combined to form straight or branched chains. Cyclic Hydrocarbons are those whose molecules have carbon atoms that are combined to form one or more rings or various other structures. Aliphatic (non-cyclic or Acyclic) Hydrocarbons are those whose molecules have carbon atoms that are combined to form straight or branched chains. Aliphatic compounds burn readily and are toxic. b. Saturated, unsaturated, unsaturated

and

actively

A Saturated compound contain only one carboncarbon signle bond. all the four bonds of carbon are fully utilised and no more hydrogen or other atoms can attach to it. Thus, they can undergo only substitution reactions. (aka ALKANES) An Unsaturated Compound contain one double covalent bond between carbon atoms or a triple covalent bond between carbon atoms. the bonds of carbon are not fully utilised by hydrogen atoms, more of these can be attached to them. Thus, they undergo addition reactions as they have two or more hydrogen atoms less than the saturated hydrocarbons.

miscibility of the compounds in H2SO4  indicates whether the sample is a very weak base (can be protonated) or a neutral compound (cannot be protonated).The dissolution of compounds in H2SO4  may also produce large amounts of heat and/or a change in the color of the solution, precipitation or any combination of these. * H2SO4 -soluble (very weak base)Esters, Ketones, Alkenes, Aldehydes Alcohols - insoluble (neutral compound)Alkanes, Aryl halides, Alkyl halides, most aromatic hydrocarbons The ignition test was performed to indicate the presence of unsaturation or high carbon to hydrogen ratio. Generally, high carbon to hydrogen ratio equals high luminosity and the more the flame produces black smoke or soot. The degree of luminosity can be assessed by the presence of yellow flame and soot. Aromatic compounds burn with sooty flame due to the incomplete combustion which causes the formation of an unburned carbon. Aromatic compound is greater than unsaturated hydrocarbon, and unsaturated hydrocarbon is greater than saturated hydrocarbon in terms of degree of luminosity. Complete combustion is indicated by a blue flame (non-luminous) and there is more heat than light; hence the carbon is completely oxidized. On the other hand, incomplete combustion is indicated by a yellow flame(luminous) and there is much light than heat; hence the carbon is not completely oxidized. 

c. Aliphatic and aromatic 

Aliphatic compounds in organic chemistry are the non aromatic compounds. They can be either cyclic or acyclic. Alkanes, alkenes, alkynes and their derivatives are mainly considered as aliphatic compounds. These can have branched or linear structures and can be either saturate (alkanes) or unsaturated (alkenes and alkynes).

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An aromatic compound contains a set of covalently-bound atoms with specific characteristics: A delocalized conjugated π system, most commonly an arrangement of alternating single and double bonds. Coplanar structure, with all the contributing atoms in the same plane. Contributing atoms arranged in one or more rings 2.

Give the rxn and general mechanism of: a. Baeyer ’ s Test b. Bromine Test (review org notes) c. Nitration (review org notes) d. The physical characteristics of each sample were noted. All the organic compounds use dare clear, colorless liquid. Each compound has their own characteristic odor that makes them distinguishable from the others. The solubility or

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Complete Combustion C xHY + O2 → CO2 + H2O Incomplete Combustion C xHY + O2 → CO2 + H2O + C(soot) + CO

The test for Active Unsaturation was accomplished in two ways: Baeyer’s test and Bromine test. Both determine the presence of double bond in each organic compound. In the Baeyer’s test, the reagent used was 2%KMnO4  solution. The positive result that must be obtained in the test is the decolorization of a purple solution followed by formation of a brown precipitate. All but cyclohexene gave a negative result to the test. It indicates that cyclohexene is positive for the active unsaturation test and that it contains double bond in its chemical structure. In the reaction, Mn7+ is reduced to Mn4+which means that alkene is oxidized to a diol in the process of redox reaction. Alkenes react with potassiumpermanganate (KMnO4) to give a diol and MnO2. Aromatic compounds do not react in this test because of their stability. Cyclohexene + KMnO4(purple) → 1,2 –   cyclohexanediol (colorless) + KMnO2(brown)

The reagent used in Bromine test was 0.5% Br2 in CCl4. A positive result is obtained by decolorization of an orange solution. In this case, cyclohexene decolorized immediately and became a clear solution while the other compounds still needed exposure to UV lighting order to decolorize. From there, the test readily gave a positive result to cyclohexane which makes it actively unsaturated in the two different tests performed. The alkenes react with Br2 to form a trans-dibromoalkane. The reaction involves electrophilic addition. Aromatic compounds do not react because of their stability; however, they will react slowly upon using FeBr3 or through the action of UV light. The test for Aromaticity was performed through Nitration. The reagents used were HNO3 and H2SO4. A positive result in the testis obtained when a yellow oily layer is formed. Benzene and toluene gave a positive result and therefore the two compounds are considered aromatic. Other than that, the two compounds are also cyclic and planar in their chemical structure and they obey Huckel’s rule that is why they are considered aromatic compounds. The H2SO4 acts as a catalyst and facilitates the formation of nitronium ion (NO2+), an electrophile. One hydrogen in the benzene ring is substituted by the nitronium ion that is why the reaction involves electrophilic substitution 

HNO3 + H2SO4 → NO2+ + 2H2SO4- + H3O+

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Benzene + NO2+ → nitrobenzene

The last test performed was Basic Oxidation,a test for alkylated aromatics or arenes. The reagents used were 2% KMnO4 and 10%NaOH. A positive result in the test will produce a violet solution (MnO 4) or brown precipitate

(MnO2).

NaOH

provides

a

basic

environment. The alkyl group of the aromatic compound is oxidized to a carboxylic acid, therefore involves a redox reaction. Mn7+is reduced to Mn6+/4+ depending on the extent of the reaction. 

Methylbenzene + KMnO4→ benzoic acid + MnO4

LAB 8  CLASSIFICATION TESTS FOR ORGANIC HALIDES  – 

1. Differentiate: Primary carbon atom  - bonded to one other carbon atom Secondary carbon atom  - bonded to two other carbon atoms Tertiary carbon atom  - bonded to three other carbon atoms

Quaternary carbon atom  - bonded to four other carbon atoms