Properties of Organic and Properties of Organic and Inorganic CompoundsInorganic Compounds

Experiment 1Chem 121 Organic Chemistry Laboratory

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What is ORGANIC CHEMISTRY?

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IntroductionIntroductionVital force – ‘vitalism’Friedrich Wohler overthrew vitalism

◦Synthesis of urea from ammonium cyanate

Distinguishing feature: organic compounds all contain the CARBON atom

NH4+

C-

N

O

NH2 NH2

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What is ORGANIC What is ORGANIC chemistry?chemistry?the study of carbon containing

compounds◦Other elements in organic

compounds: H, O, N, S, P, Cl, Br, I and other transition metals

Why Carbon?◦Can share four valence electrons◦Form strong covalent bonds◦Form rings and long chains, e.g.

benzene and DNA4

Definition of termsDefinition of termsIonic compounds: compounds made

up of a metal cation and a nonmetal anion◦e.g. NaCl, KNO3

Intramolecular forces of attraction: forces existing within molecules that holds the atoms together◦e.g. Ionic bond, covalent bond, metallic

bondIntermolecular forces of attraction:

forces existing between molecules5

Intermolecular Forces of Intermolecular Forces of AttractionAttractionIon-dipole

◦Between an ionic compound and a polar compound e.g. NaCl dissolved in water

Dipole-dipole◦Between two polar compounds

e.g. HCl dissolved in water

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Hydrogen Bonding◦Requirement: H atoms bonded to F,

O, N◦Strongest intermolecular force◦e.g. NH3 in H2O

London dispersion forces/van der Waals forces◦Between two NONPOLAR

compounds◦Weakest intermolecular force;

present in all organic molecules

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The larger the size of the organic compound, the

larger the London dispersion forces.

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Properties of Organic Properties of Organic CompoundsCompoundsFlammable

◦Due to the C-C bond energies in organic compounds

◦Energy released is in the form of heat

Ethanol vs. Water◦Ethanol – produces the distinct blue

flame◦Water – smothers flame instead of

generating one

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Charring ◦also known as burning, scorching◦organic compounds are sensitive to

heat◦End result of charring: elemental C

Sucrose• disaccharide• common ingredient in sweet foods like ice cream, candy• also works as a food preservative

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IMF of sucrose: London dispersion force

IMF of NaCl and CaCO3: no intermolecular force, but intramolecular (IONIC BOND)

Remember always: Intramolecular forces are way STRONGER than intermolecular forces.

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Solubility◦relies on the intermolecular forces of

organic compounds◦‘like dissolves like’◦Polar solvents dissolve in polar solutes.◦Nonpolar solvents dissolve in nonpolar

solutes.◦Organic compounds = mostly nonpolar

It only follows that most organic compounds are soluble in organic solvents.

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Naphthalene in ether

◦ No ionic bonds, just pure London dispersion forces

Naphthalene in water

Water is capable of hydrogen bonding; naphthalene cannot

CH3

O

CH3

H

O

H

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Electrical ConductivityElectrical Conductivity

Electrical conductivity is only possible when a compound contains charged particles (i.e. an electrolyte)◦e.g. NaCl, NaNO3 are electrolytes

Since most organic compounds are molecular, not ionic, it does not conduct electricity.

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1 M sucrose

1 M ethanol

CH3 O

H

1 M NaCl

hexane

Na+

Cl-

CH3 CH3

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SummarySummaryOrganic chemistry is the study of

carbon compounds.Organic compounds have the ff

properties:◦Flammable◦Combustible◦Immiscble in polar solvents like

water◦Non-electrolytes; do not conduct

electricity16