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Course lecturer :

Jasmin Šutković

28th November 2015

Organic Chemistry – FALL 2015

Lecture 3 :Introduction to Organic Chemistry

Contents International University of Sarajevo

11.1 Introduction to Organic Chemistry11.2 Characteristic Features of OrganicCompounds11.3 Shapes of Organic Molecules11.4 Drawing Organic Molecules11.5 Functional Groups11.6 Properties of Organic Compounds11.7 FOCUS ON HEALTH & MEDICINE:Vitamins

Book chapter 11

Introduction

In this lecture we learn about the characteristic features of organic molecules.

What is organic chemistry?

Organic chemistry is the study of compounds that contain the element carbon.

Clothes, foods, medicines, gasoline, refrigerants, and soaps are composed almost solely of organic compounds.

Some, like cotton, wool, or silk are naturally occurring; that is, they can be isolated directly from natural sources.

We will start with smaller molecules, small number of C atoms.

Mehane (CH4) and Ethanol (C2H5OH)

Ethanol produced in Lab, Methane naturally.

CHARACTERISTIC FEATURES OF ORGANIC COMPOUNDS

All organic compounds contain carbon atoms and most contain hydrogen atoms. Carbon always forms four covalent bonds, and hydrogen forms one covalent bond.

Common fetures ?

Bonding depends on the atom number around C

The most common multiple bond between C and a heteroatom is carbon – oxygen double bond.

Carbon forms 4 stable bonds with itself and other elements. Carbon atoms bind together to fotm RINGS or CHAINS

Shapes of Organic molecules

Recall section 4.6 = the most stable structural arranement keeps its groups as far away from each other = VSEPR theory

All carbons having 4 single bonds are tetrahedral ! Exp : ethane

IUPAC name : ETHYNE = C2H2

IUPAC name : ETHENE = C2H4

Drawing organic molecules

Because organic molecules contain many atoms we need to find the best way to simplify their strucures.

TWO ways are used :

Condensed structures and Skeleton structures

• Condensed structures used for molecules having a chain of atoms bound together, rather than a ring.

• Skeleton structures used for molecules having a both, chain and ring of atoms.

Condensed structures

Following rules are used :

Skeletal structures

Functional groups

More than 20 milion organic compounds are known, most of the have C, H and O atoms.

Many organic molecules have also other structural feautures – called functional groups !

Functional group determines the molecule shape and therefore its function !

Functional group in this case in OH (hydroxyl group)

Hydrocarbons

Are organic molecules that contain only C and H elements.

Alkanes – single bonds Alkenes – double bond Alkynes – triple bond Aromatic hydrocarbons – benzane ring (6 C

atoms and 3 double bonds )

All hydrocarbons other than Alkanes contain multiple bonds. Alkanes, which have no functional groups and therefore no reactive sites, are notoriously uncreative except under very drastic conditions.

For example, polyethylene is a synthetic plastic and high molecular weight Alkane, consisting of long chains of CH2 groups bonded together, hundreds or even thousands of atoms long.

Polyethylene

Hydrocarbons that have NO other functional groups – no reactive sites are very UNREACTIVE in nature.

Exp :Polyethylene

COMPOUNDS CONTAINING A SINGLE BOND TO A HETEROATOM

Several types of functional groups contain a carbon atom singly bonded to a heteroatom.

Common examples include alkyl halides, alcohols, ethers, and amines, as shown in Table 11.4.

Molecules containing these functional groups may be simple or very complex. It doesn’t matter what else is present in other parts of the molecule.

Always dissect it into small pieces to identify the functional groups.

For example, diethyl ether, the first general anesthetic, is an ether because it has an O atom bonded to two C’s.

Tetrahydrocannabinol (THC), the active component in marijuana, is also an ether because it contains an O atom bonded to two carbon atoms. In this case the O atom is also part of a ring.

COMPOUNDS CONTAINING A C=O GROUP

Many different kinds of compounds contain a carbon–oxygen double bond (C=O, carbonyl group), as shown in Table 11.5.

Carbonyl compounds include aldehydes, ketones, carboxylic acids, esters, and amides. The type of atom bonded to the carbonyl carbon—hydrogen, carbon, or a heteroatom—determines the specific c class of carbonyl compound.

Aldehydes, Carboxylic acid and Esters

PROPERTIES OF ORGANIC COMPOUNDS

Because organic compounds are composed of covalent bonds, their properties differ a great deal from those of ionic inorganic compounds.

This causes lower melting points to organic molecules, many organic molecules are liquid (some gaseous) in rooms temperature (ionic molecules are solid)

POLARITY

Are organic compounds polar or nonpolar ?

That depends.

Like other covalent compounds, the polarity of an organic compound is determined by two factors:

the polarity of the individual bonds and the overall shape of the molecule.

The polarity of an individual bond depends on the electronegativity of the atoms that form it.

SOLUBILITY

Understanding the solubility properties of organic compounds allows us to understand many interesting phenomena.

One rule governs solubility: “Like dissolves like.”

Three facts can then be used to explain the solubility of organic compounds :

Three compounds—hexane, ethanol, and cholesterol—illustrate these principles. All of these compounds are organic and therefore soluble in an organic solvent like diethyl ether (CH3CH2OCH2CH3).

Their water solubility depends on their polarity and size.

Since hexane (CH3CH2CH2CH2CH2CH3) is a nonpolar hydrocarbon, it is insoluble in water.

Ethanol (CH3CH2OH), on the other hand, is water soluble because it is small and contains a polar OH group.

FOCUS ON HEALTH & MEDICINE

Vitamins

Vitamins are organic compounds needed in small amounts for normal cell function.

Our bodies cannot synthesize these compounds, so they must be obtained in our diet. Most vitamins are identified by a letter, such as A, C, D, E, and K. There are several different B vitamins, though, so a subscript is added to distinguish them—for example, B1, B2, and B12.

Vitamins are classified on the basis of their solubility properties.

Vitamin A

Vitamin A, or retinol, is an essential component of the vision receptors in the eyes.

It also helps to maintain the health of mucous membranes and the skin, so many anti-aging creams contain vitamin A.

A deficiency of this vitamin leads to a loss of night vision.

Vitamin C

Although most animal species can synthesize vitamin C, humans, some animals obtain this vitamin from dietary sources.

Citrus fruits, strawberries, tomatoes, and sweet potatoes are all excellent sources of vitamin C.

Vitamin C, or ascorbic acid, is important in the formation of collagen, a protein that forms the connective tissues of skin, muscle, and blood vessels.

A deficiency of vitamin C causes scurvy, a common disease of sailors in the 1600s who had no access to fresh fruits on long voyages.

Readings

Book Chapter 11

Book Page : 322-354