Introduction to Organic Chemistry

Bettelheim, Brown, Campbell and Farrell

Chapter 10

Organic ChemistryCompounds that contain carbon– Other elements: H, O, N, Cl, F, Br, I, P, S

Most compounds known are organic (> 85 %)

NOT just from living systems (biochemistry)• Wohler synthesized urea from inorganic compounds• Vital Force Theory disprove

NH4Cl AgNCO H2N-C-NH2

OAgCl+ heat +

Ammoniumchloride

Silvercyanate

Urea Silverchloride

Biochemistry: Chemistry of Living Systems

• Biochemical MoleculesBiochemical Molecules– Carbohydrates – Lipids – Proteins and enzymes – Nucleic acids – Hormones– Vitamins– Almost all chemicals in living systems are organic

compounds

• Biochemical molecules are BIG organic molecules

Organic vs. Inorganic Compounds

Organic Compounds Inorganic Compounds

Bonding is almost entirely covalentMay be gases, liquids, or solidswith low melting points (lessthan 360°C)Most are insoluble in waterMost are soluble in organic solventssuch as diethyl ether, toluene, and dichloromethaneAqueous solutions do notconduct electricityAlmost all burn

Reactions are usually slow

Most have ionic bondsMost are solids with high melting points

Many are soluble in waterAlmost all are insoluble in organic solvents

Aqueous solutions conductelectricityVery few burn

Reactions are often very fast

Table 11.1

Organic Structures & Formulas

Molecular Formula: Molecular Formula: shows only the number of each type of atom

Structural Formula:Structural Formula: shows atoms and the bonds that connect them

Lewis Structure: Lewis Structure: shows the atoms, bonds and unshared electron pairs (valence electrons only)

Organic Compounds—Atoms & Bonds

• For neutral (uncharged) organic compounds– carbon: carbon: four covalent bonds and no unshared pairs of

electrons– hydrogen:hydrogen: one covalent bond and no unshared pairs

of electrons– nitrogen:nitrogen: three covalent bonds and one unshared pair

of electrons– oxygen:oxygen: two covalent bonds and two unshared pairs

of electrons– a halogen:a halogen: one covalent bond and three unshared

pairs of electrons

Number of bonds formed

Carbon 4 bonds

Nitrogen 3 bonds

Oxygen 2 bonds

Hydrogen 1 bond

Halogen 1 bond

Organic StructureVSEPR model:VSEPR model: the most common bond angles

are 109.5°, 120°, and 180°

H-C-C-H

H

H H

H H

HC C

H

HH-C C-H

H-C-O-H

H

H

HC O

HH-C-N-HH

HH

HN

H HC

H-C-C-Cl

H

H H

H

Ethane(bond angles

109.5°)

Ethylene(bond angles

120°)

Acetylene(bond angles

180°)

Methanol(bond angles

109.5°)

Formaldehyde(bond angles

120°)

Methanamine(bond angles

109.5°)

Methyleneimine(bond angles 120°)

Chloroethane(bond angles

109.5°)

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Organic Chemistry

• Chemistry of compounds containing C– Over 95% of known compounds are organic

• What makes C special?– Forms stable bonds with other C atoms

• Can form bonds to up to 4 other atoms• Can form chains, rings, many shapes

– Can form stable bonds with H, O, N, F, Cl, Br, I

Bonding of Carbon

• C has 4 valence electrons

• Would expect 2 s and 2 p electrons

• Actually see 4 “equivalent” bonds for tetrahedral C

• Explained by “hybrid orbitals”

Methane – Tetrahedral geometry

s and p Orbitals

• Orbitals have definite shapes and orientations in space

(insert Fig 2.11 of text)

(if it will not all fit on one screen, put part (a) on one screen and part (b) on the next)

Hybrid Orbitals—s and p combinationsHybrid Orbitals—s and p combinations

Functional Groups• Part of an organic molecule that undergoes

chemical reaction– “Business end” of molecule

• Functional groups are important – Undergo the same types of chemical reactions no

matter in which molecule they are found– Determine chemical and physical properties of

compound– Basis for organizing organic compounds into families– Used in naming organic compounds

Some Important Functional Groups

-OH

-NH2

-C-HO

-C-O

CH3CH2OH

CH3CH2NH2

CH3CHO

CH3CCH3

O

CH3COHO

-C-OHO

Example

Alcohol

Amine

Aldehyde

Ketone

Carboxylic acid

Ethanol

Ethanamine

Ethanal

Acetone

Acetic acid

NameFamilyFunctionalgroup

Alcohols• Alcohol:Alcohol: contains an OH (hydroxyl) group

bonded to a tetrahedral carbon atom

– may be primary (1°), secondary (2°), or tertiary (3°)

CH3-C-OH

H

HCH3-C-OH

CH3

HCH3-C-OH

CH3

CH3

A 1° alcohol A 3° alcoholA 2° alcohol

R-C-O-HR

RCH3CH2OH

H

HH

HH-C-C-O-H

Structuralformula

Functional group(R = H or carbon

goup

Condensedstructuralformula

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Amines• Amine:Amine: a compound containing an amino amino

groupgroup– the amino group may be primary (1°),

secondary (2°), or tertiary (3°)

CH3NH

CH3

CH3NH2 CH3NCH3

CH3

(CH3)3N(CH3)2NH

Methylamine(a 1° amine)

Dimethylamine(a 2° amine)

Trimethylamine(a 3° amine)

or or

Aldehydes and Ketones• Both contain a C=O (carbonyl) groupC=O (carbonyl) group

– aldehyde:aldehyde: contains a carbonyl group bonded to a hydrogen; in formaldehyde, the simplest aldehyde, the carbonyl group is bonded to two hydrogens

– ketone:ketone: contains a carbonyl group bonded to two carbon atoms

CH3CHO O

CH3CCH3C-C-HR

R

ROC-C-C

O

RR

RR

R R

Functionalgroup

Functionalgroup

Acetaldehyde(an aldehyde)

Acetone(a ketone)

Carboxylic Acids

• Carboxylic acid:Carboxylic acid: a compound a compound containingcontaining a -COOH (carboxyl: carbcarbonyl + hydroxyloxyl) group – in a condensed structural formula, a

carboxyl group may also be written -CO2H.

RCOHO

CH3COHO

Functionalgroup

Acetic acid(a carboxylic acid)

• Biochemical molecules –are just BIG organic molecules

–react like organic molecules

• Need to understand organic chemistry in order to understand and appreciate biochemistry