[PHA 615 LAB] Experiment #3 - Classification Tests for Hydrocarbons, Organic Halides, and Amines

These compounds are composed entirely of C and H atoms that are arranged and bonded in specific ways.

Hydrocarbons

What are the two general classifications of organic compounds?

- Hydrocarbons

- Hydrocarbon Derivatives

What are the the two general classifications of hydrocarbons?

- Aromatic

- Aliphatic

What are the the two general classifications of aliphatic hydrocarbons?

- Saturated (Cyclic or Acyclic)

- Unsaturated (Alkene or Alkyne)

What are the factors affecting the physical and chemical properties of organic compounds?

- Molecular Geometry

- Presence of Functional Groups

- Number of Carbon Atoms and Branching

- Intermolecular Force of Attraction (IMF)

- Aromaticity

What is the molecular geometry of an sp3 carbon?

Tetrahedral

What is the molecular geometry of an sp2 carbon?

Trigonal planar

What is the molecular geometry of an sp carbon?

Linear

What are some examples of polar functional groups?

- Hydroxy (Alcohols, Phenols)

- Mercapto (Thiol, Sulfides)

- Halo (Organic halides)

- Carbonyl (Aldehydes, Ketones)

- Carboxyl (Carboxylic acid and its derivatives)

What generally is the polarity of hydrocarbons?

Non-polar

How does the number of carbons affect the polarity of a compound?

More carbons = Higher hydrophobicity = LESS POLAR

and vice versa

How does branching in a carbon chain of a compound affect its polarity?

More branching = Shorter HC length = Lower hydrophobicity = LESS POLAR

and vice versa

What are the three intermolecular forces of attraction?

- Hydrogen bonding

- Dipole-dipole

- London Dispersion Forces

What functional groups exhibit hydrogen bonding?

- Ketones and Aldehydes (C=O)

- Carboxylic acid (COOH) and derivatives

- Alcohol (OH)

- Amine (NH2)

What functional groups exhibit dipole-dipole?

- Ketones and Aldehydes (C=O)

- Carboxylic acid (COOH) and derivatives

- Alcohol (OH)

- Amine (NH2)

- Halides (X)

- Thiols (SH)

What functional groups exhibit LDF?

Pure HC

- Alkanes

- Alkenes

- Alkynes

What are the characteristics of an aromatic compound?

- Cyclic

- Planar

- Conjugated double-bonds

- Follows Huckel's rule

It predicts that a planar cyclic molecule is aromatic if it has 4n + 2 π electrons, where 'n' is an integer.

Huckel's Rule

How does IMF affect BP and MP?

Stronger IMF = Higher BP/MP

How does the presence of polar functional groups affect BP and MP?

More polar functional groups = Stronger H-bond (IMF) = Higher BP/MP

How does the number of carbons affect BP and MP?

More carbons = Stronger LDF (IMF) = Higher BP/MP

How does branching affect BP and MP?

More branching = Lower BP/MP

How does melting point relate to solubility?

Inversely Proportional

Higher MP = Lower Solubility

In isomers, which is more soluble?

Cis- isomer forms are more soluble than trans- isomers.

How does molecular weight relate to solubility?

Indirectly Proportional

Higher molecular weight = Stronger IMF = Lower solubility

What is the solubility of hydrocarbons in organic solvents?

Generally soluble

What is the solubility of hydrocarbons in water?

Insoluble

How does the number of carbons relate to water solubility?

Inversely Proportional

More carbons = Higher hydrophobicity = Lower polarity = Lower water solubility

How many carbons in an organic compound is generally insoluble in water?

More than 5 carbons

What happens to the water solubility of a compound as the percentage of HC in a given molecule increases?

Water (polar solvent) solubility DECREASES

What happens to the ether solubility of a compound as the percentage of HC in a given molecule increases?

Ether (organic/non-polar solvent) solubility INCREASES

(True/False) A straight-chain compound is more soluble than branched-chain compound.

False

- BRANCHED-CHAIN is more soluble.

(True/False) The position of the functional group can also affect solubility.

True

What reagent is used in solubility test?

Concentrated Sulfuric Acid (H2SO4)

Procedure for Solubility Test in H2SO4

1. Place 1-mL of H2SO4 in test tube

2. Add 1-2 drops of the sample to their assigned test tube

3. Determine which sample is MISCIBLE or IMMISCIBLE

What does the solubility test determine?

It is an HC compound must be immiscible in water.

What is the result of the solubility test in H2SO4 of the following compounds: Heptane, Hexane, Cyclohexane, Cyclohexene, Benzene, Toluene

All are insoluble EXCEPT cyclohexene (soluble).

What test is generally used to classify alipatic from aromatic hydrocarbons?

Ignition Test

Procedure for Ignition Test

1. Place 3-5 drops of sample in a small evaporating dish.

2. Light the sample with a match. Observe the results.

3. Observe for sample's flammability, color of flame, and burning time

What properties of the sample should be observed during ignition test?

- Flammability

- Color of flame

- Burning time

It is a measure of how easily a substance bursts into flame through fire or combustion.

Combustibility

It is the ease with which a combustible substance can be ignited causing fire, combustion, or even explosion.

Flammability

What is the chemical reaction for complete combustion?

CxHy + O2 -> CO2 + H2O

What is the chemical reaction for incomplete combustion?

CxHy + O2 -> CO2 + CO + C + H2O

+ formation of soot

It is a black powdery or flaky substance consisting largely of amorphous carbon, produced by the incomplete burning of organic matter.

Soot

How does the number of hydrocarbons in a compound affect combustion, luminosity, and the formation of soot?

More hydrocarbons

- Lower combustion

- Higher luminosity

- More soot formed

What is the result of the ignition test for aliphatic hydrocarbons?

Yellow flame with little or no soot at all

What is the result of the ignition test for aromatic hydrocarbons?

Yellow flame with soot

What are the three tests of unsaturation?

- Baeyer's Test

- Bromine Test

- Iodine Test

Procedure for Baeyer's Test

1. Place 5 drops of the sample in a clean and dry test tube.

2. Add 2 drops of 2% KMnO4. Observe for decolorization.

3. Observe as for the formation of brown sludge or suspension.

What properties of the sample should be observed during Baeyer's test?

- Decolorization

- Formation of brown sludge or suspension

In Baeyer's test, the solution decolorizes immediately if it happens within?

1 minute

What is used as the standard for decolorization in Baeyer's test?

Water

What reagent is used in Baeyer's test?

Potassium permanganate (KMnO4)

What is formed during Baeyer's test for a positive result?

Brown suspension/sludge

What reaction mechanism is observed in Baeyer's test?

Oxidation Reaction (Mild)

What compounds does the Baeyer's test detect?

Active unsaturation / alkenes and alkynes

Procedure for Bromine Test

1. Place 5 drops of the sample in a clean and dry test tube.

2. Add 10 drops of 0.5% Br2. in CCL4 reagent. Shake. Observe for decolorization.

3. Observe as for the formation of bromine discharge (brownish red).

4. Place a moistened blue litmus paper on a glass rod and place it across the mouth of the test tube. Note the color change.

What properties of the sample should be observed during the Bromine test?

- Decolorization

- Formation of bromine discharge (brownish red)

What is formed during Bromine test for a positive result?

Brownish red of bromine discharge (decolorization)

What reagent is used in Bromine test?

Br2/CCl4

What reaction mechanism is observed in the Bromine test?

Electrophilic Addition (AE) Reaction

What compounds does the Bromine test detect?

Double/Triple Bonds

What properties of the sample should be observed during Iodine test?

Formation of tan-colored solid while retaining the color of the I2 solution

What reagent is used in Iodine test?

Iodine (I2) solution

What reaction mechanism is observed in Iodine test?

Addition reaction

What compounds does the Iodine test detect?

Alkenes/Alkynes

Test that uses KMnO4 and is a form of oxidation reaction which forms a brown suspension/sludge. It detects the presence of active unsaturation like in alkenes and alkynes.

Baeyer's Test

Test that uses Br2 in CCl4 to confirm the presence of double/triple bonds. It is an addition reaction in which the Br2 solution is decolorized when mixed with unsaturated compounds.

Bromine Test

Test that uses I2 solution and is also an addition reaction used to confirm the presence of alkene/alkynes. The positive result for this test is the formation of a tan-colored solid while retaining the color of the I2 solution.

Iodine Test

Procedure for Nitration Reaction

1. Place 5 drops of the sample in a clean and dry

test tube.

2. Add 8 drops of the nitrating mixture.

3. Shake vigorously for complete mixing. Observe

for a yellow oily layer or droplet

4. Dilute the resulting solution with 2 drops of

water. Observe for reaction.

5. If no observed reaction, Place the test tube in a

water bath for 10 mins.

6. Dilute with 20 drops of water. Observe for

results.

It is a common substitution reaction for aromatic molecules. It is used to detect the presence of benzene rings in a compound.

Nitration

What compounds does the Nitration reaction detect?

Aromatic / Benzene

What properties of the sample should be observed during the Nitration reaction?

Formation of yellow oily layer confirms the presence of a benzene ring

How does the presence of electron-donating groups (e.g. CH3) on the benzene ring affect its reaction during nitration reaction?

Faster reaction

What reaction mechanism is observed in Nitration test?

Electrophilic Substitution

What reagents is used in nitration test?

HNO3 in H2SO4

(True/False) Benzene reacts faster than toluene.

False

- Toluene is a CH3 group; thus, it has a FASTER reaction than benzene.

Procedure for Basic Oxidation

1. Place 4 drops of the sample in a clean and dry test tube.

2. Add 8 drops of 2% KMnO4 and 3 drops of 10% NaOH.

3. Place the test tubes in a water bath for 20

minutes. Observe for color change or brown

precipitate.

This test uses KMnO4 in NaOH solution and is often called mild oxidation.

Basic Oxidation

What reagents is used in basic oxidation test?

2% KMnO4 in 10% NaOH

Basic oxidation test detects the presence of what compounds?

- Alkene

- Benzylic carbon (must have benzylic hydrogen)

Both are susceptible to oxidation.

What properties of the sample should be observed during Basic Oxidation test?

Brown precipitate/suspension

These are organic compounds that contain a halogen moiety (-X = F, Cl, Br, and I).

Organic halides/Haloalkanes

Haloalkanes are categorized based on?

Type of alpha carbon they possess in the structure