Chapter 1Organic Chemistry

Organic chemistry: the study of the compounds of carbon.Organic compounds are made up of carbon

and only a few other elements.chief among these are hydrogen, oxygen,

and nitrogenalso present are sulfur, phosphorus, and

halogens (fluorine, chlorine, bromine, or iodine)

Why Carbon?

Why is organic chemistry a separate discipline within chemistry?

The sheer number of organic compounds Chemists have discovered or made over 10

million organic compounds and an estimated 100,000 new ones are discovered or made each year.

By comparison, chemists have discovered or made an estimated 1.7 million inorganic compounds.

Thus, approximately 85% of all known compounds are organic.

The link to biochemistryCarbohydrates, lipids, proteins, enzymes,

nucleic acids, hormones, vitamins, and almost all other chemicals in living systems are organic compounds.

Historical: scientists at one time believed that a “vital force” present in living organisms was necessary to produce an organic compound.The experiment of Wöhler in 1828 was the

first in a series of experiments that led to the demise of the vital force theory.

NH4Cl AgNCO H2N-C-NH2

OAgCl+ heat +

Ammoniumchloride

Silvercyanate

Urea Silverchloride

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

O

O

O CH2OH

OH

OH

H

CH2OH

OH

OHOH

H

H

H

H

H

H

HH

Sucrose (table sugar) Sodium chloride (table salt)

Na+ Cl-

Structure

Structural formula: shows the atoms present in a molecule as well as the bonds that connect them.

Lewis structure: A molecular representation that shows both the connections among atoms and the locations of lone-pair valence electrons.

Common bonding patterns for C, N, O, X, and H

• 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°)

::

::::

::

:

3-D structure: Shows orientation in space, using wedges and dashes.

Condensed structure: Bonds are not specifically shown.

line-angle formula: A line represents a carbon-carbon bond and a

vertex and a line terminus represent a carbon atom.

Hydrogen atoms are not shown in line-angle formulas.

CH3CH2CH2CH3CH3CH2CH3 CH3CH2CH2CH2CH3CH3CH2CH2CH3CH3CH2CH3 CH3CH2CH2CH2CH3PentaneButanePropane PentaneButanePropane

Condensedstructural

formula

Line-angleformula

Ball-and-stick model

Constitutional isomers—compounds with the same molecular formula, but with different structural formulas (different connectivity).

• For the molecular formula C4H10, two constitutional isomers are possible.

CH3CH2CH2CH3 CH3CHCH3

CH3

Butane(bp -0.5°C)

2-Methylpropane(bp -11.6°C)

Functional Groups

Functional group: an atom or group of atoms within a molecule that shows a characteristic set of predictable physical and chemical properties.

-OH

-NH2

-C-H

-C-

CH3CH2OH

CH3CH2NH2

CH3CHO

CH3CCH3

O

CH3COHO

-C-OH

Example

Alcohol

Amine

Aldehyde

Ketone

Carboxylic acid

Ethanol

Ethanamine

Ethanal

Acetone

Acetic acid

NameFamilyFunctionalgroup

CH3COCH2CH3

O-C-ORCarboxylic ester Ethyl acetate

O

O

O

O

Alcohol: contains an OH (hydroxyl) group bonded to a tetrahedral carbon atom. For example, ethanol:

R-C-O-HR

RCH3CH2OH

H

HH

HH-C-C-O-H

Structuralformula

Functional group(R = H or carbon

goup

Condensedstructuralformula

::

CH3-C-OH

H

HCH3-C-OH

CH3

HCH3-C-OH

CH3

CH3

A 1° alcohol A 3° alcoholA 2° alcohol

Amine: a compound containing an amino group.• 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

Carbonyl group: C=O

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

• 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 acid: a compound containing a -COOH (carboxyl: carbonyl + hydroxyl) group.

• In a condensed structural formula, a carboxyl group may also be written -CO2H.

RCOHO

CH3COHO

Functionalgroup

Acetic acid(a carboxylic acid)

Carboxylic ester: a derivative of a carboxylic acid in which the H of the carboxyl group is replaced by a carbon group.

C-O–C

O

CH3COOCH3

Functionalgroup

Methyl acetate(an ester)

CH3-C-O-CH3

O

or CH3CO2CH3or

Summary of Topics: Chapter 1

What is Organic Chemistry? Structural formulas

Lewis, condensed, line-angle Constitutional isomers Functional groups