Experiment 6 and 7 - Classification Tests for Organic Compounds

Classification test of organic compounds

mrsantiago (Chem 200 lab, AY 2014-2015)

Physical and chemical properties

Physical properties

• Physical state (solid, liquid, gas)

• Color, odor

• Solubility

Chemical properties

• Reaction to litmus paper

• Chemical tests

mrsantiago (Chem 200 lab, AY 2014-2015)

mrsantiago (Chem 200 lab, AY 2014-2015)

mrsantiago (Chem 200 lab, AY 2014-2015)

Solubility in water

mrsantiago (Chem 200 lab, AY 2014-2015)

mrsantiago (Chem 200 lab, AY 2014-2015)

mrsantiago (Chem 200 lab, AY 2014-2015)

mrsantiago (Chem 200 lab, AY 2014-2015)

Factors affecting H2O solubility

• Intermolecular forces of attxn

(H bonding>dipole>hydrophobic)

• No. of carbon atoms (>5C insoluble; C, hydrophobicity, less polar )

• Length of HC chain

• Branching (branching, length, hydrophobic)

• Presence of polar functional groups

mrsantiago (Chem 200 lab, AY 2014-2015)

FUNCTIONAL GROUPS THAT MAY CAUSE IMFA

• Functional groups that can participate in H-bonding – Carboxyl – Carbonyl – Hydroxyl – Amino

• Functional groups that can participate Dipole-Dipole Interaction – Hydroxyl – Amino – Halo – Mercapto – Carbonyl – Carboxyl

• Functional groups that can participate in hydrophobic interaction – hydrocarbon

mrsantiago (Chem 200 lab, AY 2014-2015)

ACID AND BASE

• Bronsted Acid and Bases

– Acid: proton donor

– Base: proton acceptor

• Lewis Acid and Bases

– Acid: e- acceptor

– Base: : e- donor

mrsantiago (Chem 200 lab, AY 2014-2015)

Solubility in 5% HCl

mrsantiago (Chem 200 lab, AY 2014-2015)

Solubility in 5% HCl

• Basicity

• Availability of electron pairs

(the more available the electrons, the more readily they can be donated to form a new bond to the proton and, the stronger base)

mrsantiago (Chem 200 lab, AY 2014-2015)

• Electronegativity ( CH3- > NH2

- > HO- > F-) the more e- the atom donating the electrons , the less willing it is to share those electrons with a proton, so the weaker the base.

Solubility in 5% HCl

mrsantiago (Chem 200 lab, AY 2014-2015)

• Size (F- > Cl- > Br- > I- )

the larger the atom the weaker the H-X bond and the lower the electron density making it a weaker base

• Resonance (RO- > RCO2- )

electrons less available when they localised on a specific atom

Solubility in 5% NaOH

• ACIDITY

• Electronegativity (HF > H2O > NH3 > CH4 )

the more electronegative the anionic atom in the conjugate base, the better it is at accepting the negative charge, stronger acid.

• Size (HI > HBr > HCl > HF)

The size weakens the bond H-X, weaker acid

• Resonance (RCO2H > ROH)

mrsantiago (Chem 200 lab, AY 2014-2015)

Acidity trend of common organic acids and bases

mrsantiago (Chem 200 lab, AY 2014-2015)

Sample Physical state Solubility in H20

Solubility in HCl (Basic)

Solubility in NaOH (Acid)

Cyclohexane L (gas-like) - - -

Dichloromethane L (Cl-like) - - -

Ethanol l (wine-like) + + +

Phenol l (pungent - - +

Benzoic acid s (pungent) - - + (wa)

Ethyl acetate l (plastic balloon-like)

+ + +

Ethyl amine l(fish-like) + + -

mrsantiago (Chem 200 lab, AY 2014-2015)

Summary (Expt 6)

FLAMMABILITY/COMBUSTIBILITY OF ORGANIC COMPOUNDS

• Complete Combustion:

CxHy + O2 CO2 + H2O

• Incomplete Combustion:

CxHy + O2 CO2 + CO + C + H2O

• C:H ratio, combustible, luminosity, soot

mrsantiago (Chem 200 lab, AY 2014-2015)

Sample Flammability (C:H)

Hexane 6:14

Heptane 7:16

Cyclohexane 6:12

Cyclohexene 6:10

Benzene 6:6

Toluene 7:8

Solubility in conc. H2SO4

mrsantiago (Chem 200 lab, AY 2014-2015)

Solubility in conc. H2SO4

mrsantiago (Chem 200 lab, AY 2014-2015)

mrsantiago (Chem 200 lab, AY 2014-2015)

TEST FOR ACTIVE UNSATURATION

• Immediate reaction to halogenating substances such the diatomic halogen compounds (Br2, Cl2, I2 and F2)

• Easily oxidized to saturated HC

– Order of oxidation of HC: Alkyne Alkene Alkane

• Tests for Active Unsaturation:

– Br2 Test

– Baeyer’s Test

mrsantiago (Chem 200 lab, AY 2014-2015)

1. BROMINE TEST (AE) Rgt: Br2 in DCM solution

+ Result: decolorization of Br2 in DCM

mrsantiago (Chem 200 lab, AY 2014-2015)

2. BAEYER’S TEST (REDOX) Rgt: Aqueous KMnO4

+ Result: decolorization of KMnO4 and brown ppt.

mrsantiago (Chem 200 lab, AY 2014-2015)

Summary: Test for Active Unsaturation

mrsantiago (Chem 200 lab, AY 2014-2015)

Sample Baeyer’s Br2 in DCM

Hexane - -(slow)

Heptane - -(slow)

Cyclohexane - -(slow)

Cyclohexene +++ (fast) +++ (fast)

Benzene - -

Toluene - (slow) - (slow)

AROMATICITY HYDROCARBONS (HUCKLE’S RULE)

1. Cyclic

2. Planar

3. Conjugated double bonds

4. #e- = 4n + 2, where n I

mrsantiago (Chem 200 lab, AY 2014-2015)

TEST FOR AROMATICITY

• Nitration of the aromatic ring

Preparation of Nitrating Agent:

HNO3 + H2SO4 NO2+ + 2HSO4

- + H3O+ Prevents dilution of NO2

+ by absorbing water in the mixture

Nitration of the Aromatic Ring (SE)

mrsantiago (Chem 200 lab, AY 2014-2015)

Test for arenes: BASIC OXIDATION TEST

• Test for arenes (alkylbenzene)

• Oxidation of alkyl group to COOH

mrsantiago (Chem 200 lab, AY 2014-2015)

Summary (Expt 7)

mrsantiago (Chem 200 lab, AY 2014-2015)

Sample Flammability (C:H)

Solubility in H2SO4

Baeyer’s Br2 in DCM Nitration Basic Oxidation

Hexane 6:14 - - -(slow) -

Heptane 7:16 - - -(slow)

-

Cyclohexane 6:12 - - -(slow)

-

Cyclohexene 6:10 + (alkene/alkyne)

+++ (fast) +++ (fast) - +++ (fast)

Benzene 6:6 - - - +++ (fast)

Toluene 7:8 - - (slow) - (slow) +++ (fast)

- (slow)