Lesson 01: Introduction - WordPress.com · Chemistry 11, Organic Chemistry, Unit 09 1 Lesson 01:...

Chemistry 11, Organic Chemistry, Unit 09 1

Lesson 01: Introduction

To understand life (all living things) as we know it, we must first understand the chemistry of life.

The chemistry of life is often referred to as organic chemistry and organic chemistry and sometimes as carbon chemistry because organic molecules contain carbon and hydrogen. Though many organic chemicals also contain other elements, it is the carbon-hydrogen bond that defines them as organic.


There are millions of different organic molecules, each with different chemical and physical properties. The diversity of organic chemicals is due to the versatility of the carbon atom. But why is carbon such a special element?

01 Chemistry of Carbon Carbon appears in the second row of the periodic table and has four bonding electrons in its valence shell. Similar to other non-metals, carbon needs eight electrons to satisfy its valence shell. Carbon therefore forms four bonds with other atoms.


Every valence electron participates in bonding, thus a carbon atom's bonds will be distributed evenly over the atom's surface. These bonds form a tetrahedron, as illustrated below…

Organic chemicals get their diversity from the many different ways carbon can bond to other atoms. The simplest organic chemicals, called hydrocarbons, contain only carbon and hydrogen atoms; the simplest hydrocarbon, methane, contains a single carbon atom bonded to four hydrogen atoms…

But carbon can bond to other carbon atoms in addition to hydrogen, as illustrated in the molecule ethane below…

In fact, the uniqueness of carbon comes from the fact that it can bond to itself in many different ways. Carbon atoms can form…


Long Chains

Branched Chains

Rings


There appears to be almost no limit to the number of different structures that carbon can form. To add to the complexity of organic chemistry, neighboring carbon atoms can form double and triple bonds in addition to single carbon-carbon bonds…

Single bonding Double bonding Triple bonding

Keep in mind that each carbon atom forms four bonds. As the number of bonds between any two carbon atoms increases the number of hydrogen atoms in the molecule decreases (as can be seen in the diagram above).


Lesson 02: Alkanes

01 Naming Organic Molecules

In the earlier days, the conventional names for organic compounds were mainly derived from the source of occurrence. However organic chemists realized the need for a systematic naming for organic compounds since a large number of organic compounds are possible. This results in the development of a system of nomenclature by the International Union of Pure and Applied Chemistry, IUPAC. The IUPAC system of nomenclature is a set of logical rules which are aimed at giving unambiguous names to organic compounds. By using this system, it is possible to give a systematic name to an organic compound just by looking at its structure and it is also possible to write the structure of organic compound by following the systematic name for that compound.


02 Organic Molecule Structures There are four ways to represent the structure of organic molecules in two dimensions, each has its advantages and disadvantages…

molecular formula: displays only the number of each atom present and no structure

structural formula: displays all atoms and structure, is the least condensed format

condensed formula: displays structure but no bonds between atoms

skeletal formula: displays straight lines as two bonded carbons and is the most condensed format

Representing Hydrocarbon Structures

Molecular Formula

Structural Formula

Condensed Formula

Skeletal Formula

4CH

4CH none

2 6C H

3 3CH CH

3 8C H

3 2 3CH CH CH

4 10C H

3 2 2 3CH CH CH CH


The method chosen to represent molecules depends on the complexity of the compound being drawn. The more complex the compound, the more condensed the format used to draw that compound. In my notes I have chosen to use mostly the skeletal formula format.


03 Naming non-Branching Chained Alkanes

Alkanes are the first class of organic molecules and contain only carbon-carbon single bonds. The alkanes are named by combining a prefix that describes the number of carbon atoms in the molecule with the root ending "ane". The names and prefixes for the first ten alkanes are given in the following table...


Alkanes

Carbon Atoms

Prefix Alkane Name Chemical Formula

1 Meth Methane 4CH

2 Eth Ethane 2 6C H

3 Prop Propane 3 8C H

4 But Butane 4 10C H

5 Pent Pentane 5 12C H

6 Hex Hexane 6 14C H

7 Hept Heptane 7 16C H

8 Oct Octane 8 18C H

9 Non Nonane 9 20C H

10 Dec Decane 10 22C H

The molecular formula for any alkane is given by the

expression n 2n+2C H . This type of hydrocarbon is referred to

as a saturated hydrocarbon because each carbon has been bonded to the maximum possible number of other carbons.


03 Naming Branching Alkanes

Before being able to name branching alkanes we must first know how to name branches, or substituents, on branching alkanes. One possible substituent is the alkyl group...

Alkyl Substituents Alkyl groups are essentially alkanes with one hydrogen removed. Some of the more common alkyl groups are shown in the next table...


Common Alkyl Groups

Number of Carbons

Alkyl Group Name

Molecular Formula

Skeletal Structure

1

methyl-

3CH -

2

ethyl-

3 2CH CH -

3

propyl-

3 2 2CH CH CH -

3

1-methylethyl-

3 2CH CH-

4

butyl-

3 2 2 2CH CH CH CH -

4

1-

methylpropyl

3 2 3CH CHCH CH

4

2-

methylpropyl

3 22CH CHCH -

4

1,1-

dimethylethyl

3 3CH C-


Rules for Naming Branching Alkanes To name a branching alkane you must follow the following steps…

Find and name the longest continuous carbon chain.

Identify and name groups attached to this chain.

Number the chain consecutively, starting at the end nearest a substituent group.

Designate the location of each substituent group by an appropriate number and name.

Assemble the name, listing groups in alphabetical order using the full name. Note: The prefixes “di”, “tri”, “tetra” etc., used to designate several groups of the same kind, are not a consideration when alphabetizing.

Example

Chemical Formula Name

3 2 2 3 2CH CH CH CH CH

2-methylpentane


Example


3 2 2 3

2 3

CH CH CH CH CH

CH CH

3-ethylpentane

Example


3 2 3 2

2 2 3

CH CH C CH

CH CH CH

3,3-dimethylhexane


Example


3 32

2 2 3

CH CHCH CH

CH CH CH

2,3-dimethylhexane

Example


3 2 2

2 3 2

CH CH

CHCH CH CH

4-ethyl-2-methylhexane


Structural Isomerism Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. Structural isomers are molecules which have the same molecular formula but have different order of atoms.

Two Structural Isomers of 4 10C H


04 Naming Cycloalkanes

Cycloalkanes are a type of alkane that consists of one ring (monocyclic) or more rings (polycyclic) of carbons. All consist of only carbon and hydrogen atoms and are saturated because there are no multiple C-C bonds. There are two kinds of monocyclic cycloalkanes to consider in chemistry 11...

those without substituents, and

those with substituents


Naming Monocyclic Cycloalkanes (without substituents) Monocyclic cycloalkanes are named in a similar manner to their alkane counterpart of the same carbon count...

Common Monocyclic Cycloalkanes

Name Cyclo-propane

Cyclo-butane

Cyclo-pentane

Cyclo-hexane

Cyclo-heptane

Molecular Formula 3 5C H 4 8C H 5 10C H 6 12C H 7 14C H

Structural Formula

Skeletal Structure


Rules for Naming Substituted Monocyclic Cycloalkanes To name a substituted monocyclic cycloalkane you must follow the following steps…

For a single-substituted cycloalkane the ring supplies the root name and the substituent is named as usual. A location number is unnecessary.

If the alkyl substituent is larger than the ring, the ring may be named as a substituent group on the alkane.

If two different substituents are present on the ring, they are listed in alphabetical order, and the first cited substituent is assigned to carbon number 1. The numbering of ring carbons then continues in a direction (clockwise or counter-clockwise) that affords the second substituent the lower possible location number.

If several substituents are present on the ring, they are listed in alphabetical order. Location numbers are assigned to the substituents so that one of them is at carbon number 1 and the other locations have the lowest possible numbers, counting in either a clockwise or counter-clockwise direction.

The name is assembled, listing groups in alphabetical order and giving each group (if there are two or more) a location number. The prefixes “di”, “tri”, “tetra” etc., used to designate several groups of the same kind, are not considered when alphabetizing.


Example

Name

2-cyclopropylbutane

Example

Name

ethylcyclohexane


Example

Name

1-ethyl-2-methylcyclohexane


Lesson 03: Halo Alkanes

Halo refers to the halogen elements such as fluorine, chlorine, bromine and iodine. Halo alkanes are branched alkanes containing one or more halogen elements. The naming of halo alkanes is similar to the naming of attached alkyl groups. Just make sure…

If halogens are present, label fluorine as “fluoro”, chlorine as “chloro”, bromine as “bromo” and iodine as “iodo”

Use a number to indicate the position of attachment and if more than one of the same kind of halogen is present use the prefix “di”, “tri” or “tetra”

If the compound contains both alkyl and halide groups then list groups in alphabetical order. Number from the end which results in the lowest sets of numbers.

Example

Name

1-chloropropane


Example

Name

2-bromo-2-methylpropane

Example

Name

2-bromo-2-methylpropane


Lesson 04: Multiple Bonds (Alkenes and Alkynes)

The next two classes of hydrocarbons are the alkenes and the alkynes. The only difference between these two types of hydrocarbons and alkanes are the type of bond present between adjacent carbon atoms…

Bonding in Alkanes, Alkenes and Alkynes

Alkanes Alkanes Alkynes

Single Bonds Double Bonds Triple Bonds

Alkenes and alkynes are referred to as being unsaturated hydrocarbons as they have fewer hydrogens than their equivalent alkanes.


01 Alkenes Alkenes consist of molecules that contain at least one double bonded carbon pair. Alkenes follow the same naming convention used for alkanes. A prefix is combined with the ending "ene" to denote an alkene. The chemical formula for

the simple alkenes follows the expression n 2nC H . For each

carbon-carbon double bond present, there are two fewer hydrogen atoms than their alkane counterparts.


Rules for Naming Alkenes

The “ene” suffix (ending) indicates an alkene or cycloalkene.

The longest chain chosen for the root name must include both carbon atoms of the double bond.

The root chain must be numbered from the end nearest a double bond carbon atom. If the double bond is in the center of the chain, the nearest substituent rule is used to determine the end where numbering starts.

The smaller of the two numbers designating the carbon atoms of the double bond is used as the double bond locator. If more than one double bond is present the compound is named as a diene, triene or equivalent prefix indicating the number of double bonds, and each double bond is assigned a locator number.

In cycloalkenes the double bond carbons are assigned ring locations number 1 and number 2.


Example

Name

propene

Example

Name

2-butene

Example

Name

cyclohexene


Example

Name

4-methyl-2-pentene

Example

Name

3-methyl-3-hexene


02 Alkynes Alkynes are molecules that contain at least one triple bonded carbon pair. Like the alkanes and alkenes, alkynes are named by combining a prefix with the ending "yne" to denote the triple bond. The chemical formula for the simple

alkynes follows the expression n 2n-2C H . For each carbon-

carbon triple bond present, there are four fewer hydrogen atoms than their alkane counterparts.


Rules for Naming Alkynes

The “yne” suffix (ending) indicates an alkyne or cycloalkyne.

The longest chain chosen for the root name must include both carbon atoms of the triple bond.

The root chain must be numbered from the end nearest a triple bond carbon atom. If the triple bond is in the center of the chain, the nearest substituent rule is used to determine the end where numbering starts.

The smaller of the two numbers designating the carbon atoms of the triple bond is used as the triple bond locator.

If several multiple bonds are present, each must be assigned a locator number. Double bonds precede triple bonds in the name, but the chain is numbered from the end nearest a multiple bond, regardless of its nature.

In simple cycloalkynes the triple bond carbons are assigned ring locations number 1 and number 2.


Example

Name

1-butyne

Example

Name

2-butyne

Example

Name

4-methyl-2-pentyne


03 Stereoisomerism (Spatial Isomerism) Isomers, again, are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. With spatial or geometric isomers the bond structure is the same, but the positioning of atoms in space differs. Spatial isomers occur where there is restricted rotation about bonds within a molecule…

Identifying Spatial Isomers

Free Rotation? Yes. Free Rotation? No.

Are not spatial Isomers. Are spatial Isomers.

To identify a spatial isomer the old method was to use the prefixes “cis” and “trans” to refer to those species that were on the same side of a double bond or on opposite sides of a double bond respectively. Note: The “cis” / “trans” system has now been replaced with a new a new system of prefixes, the E/Z system. In this course we will follow the old “cis” / “trans” naming system…


Examples

Names

cis-2-butene

trans-2-butene

Examples

Names

cis-2-heptene

trans-2-heptene

Examples

Names

cis-3-methyl-3-hexene

trans-3-methyl-3-hexene


Lesson 05: Aromatic Compounds (Arenes)

01 Introduction

Aromatic hydrocarbons derive their names from the fact that many of these compounds in the early days of discovery were grouped because they had fragrant odors, hence the name aromatic. The current definition of aromatic compounds includes only those with a benzene ring, which is a special six carbon ring compound with three alternating single and double bonds.

Benzene Symbol

Structure Symbol


02 Confusion with Cyclohexane Due to the similarity between benzene and cyclohexane, the two are often confused with each other...

Cyclohexane VS Benzene Structure

If you were to count the number of carbons and hydrogens in cyclohexane, you will notice that its molecular formula is

6 12C H . Since the carbons in the cyclohexane ring are fully

saturated with hydrogens (carbon is bound to 2 hydrogens and 2 adjacent carbons), no double bonds are formed in the cyclic ring. In contrast, benzene is only saturated with one hydrogen per carbon, leading to its molecular formula of

6 6C H . In other words, cyclohexane is not the same as

benzene. These two compounds have different molecular formulas and their chemical and physical properties are not the same.


03 Phenyl Group Formation The phenyl group is an important group when it comes to substituting species onto a benzene ring, 6 6C H . The phenyl

group can is formed when one hydrogen is removed from a benzene ring. The resulting molecular formula for the fragment is 6 5C H .

Although the molecular formula of the phenyl group is 6 5C H ,

the phenyl group always has something attached to where the hydrogen was removed.

Phenyl Group


05 Rules for Naming Simple Aromatic Compounds The rules for naming simple aromatic compounds are a variation of naming rules learned so far...

If the attached substituent contains no more than six carbon atoms, the compound's parent name is benzene.

Identify and name the groups attached to the benzene molecule.

Number the ring consecutively, starting at the end nearest the substituent group.

Designate the location of each substituent group by an appropriate number.

Assemble the name, listing groups in alphabetical order. The lowest number should be placed on the group that is lowest on the alphabetical list. Note: The prefixes “di”, “tri”, “tetra” etc., used to designate several groups of the same kind, is not a consideration when alphabetizing.


Example

Name

methylbenzene

Example

Name

ethylbenzene


Example

Name

propylbenzene

Example

Name

1,2-dimethylbenzene


Example

Name

1,3-dimethylbenzene

Example

Name

1-ethyl-2-methylbenzene


Example

Name

1-ethyl-3-methylbenzene

Example

Name

chlorobenzene

Example

Name

2,3-dichloromethylbenzene


Example

Name

1-chloro-2,4-dimethylbenzene


Lesson 06: Functional Groups

Functional groups are groups of atoms or bonds found within organic molecules that are involved in the chemical reactions characteristic of those molecules.


Common Functional Groups

Group Name Structure Testable?

Groups Containing Hydrogen

and Carbon

alkanes

yes

alkenes

yes

alkynes yes

aromatic rings

yes

Groups Containing Halogens

alkyl halides

yes

Groups Containing

Oxygen

alcohols

yes

aldehydes

no

ketones

no

carboxylic acids

no

esters

yes

ethers

no

Groups Containing Nitrogen

amines

no

amides

no


01 Alcohols An alcohol is the result of one or more H atoms being replaced by an OH molecule in an alkane or an alkene. Methanol and ethanol are two common alcohols that are used in laboratories.

Rules for Naming Alcohols

The root name is based on the longest chain with the OH attached.

The chain is numbered so as to give the alcohol unit the lowest possible number.

The alcohol suffix is appended after the hydrocarbon suffix minus the "e"

Example

Name

3-methyl-1-butanol


Example

Name

2-butanol

Example

Name

3-pentanol


02 Aldehydes An aldehyde has one carbon double bonded to an oxygen atom and that same carbon is bonded to a hydrogen atom as well. Aldehydes are similar to organic acids, but are without the second oxygen atom. They are named by adding “-al” to the end of the common name, or by simply adding aldehyde to the end of the name.


03 Amines Amines are organic derivatives of ammonia, meaning that one, two, or three hydrocarbons in ammonia have been replaced by substituents.

Amines

Primary Secondary Tertiary


04 Carboxylic Acids Carboxylic acids are the products of the oxidation of an alcohol and have a carbon double bonded to an oxygen atom, and singly bonded to an alcohol group. The strong taste of sourdough bread comes from carboxylic acids.


05 Esters Esters are the addition of a carboxylic acid and an alcohol, with water as a by-product. Esters are known for their sweet smells. The scent of pineapple is really the ester butyl butanoate.

Rules for Naming Esters The easiest way to deal with naming esters is to recognize the carboxylic acid and the alcohol that they can be prepared from. The general ester, RCOOR' can be derived from the carboxylic acid RCOOH and the alcohol R'OH. The first component of an ester name, the alkyl is derived from the alcohol, R'OH. The second component of an ester name, the “-oate” is derived from the carboxylic acid, RCO2H.

Alcohol component: The root name is based on the longest chain containing the OH group. The chain is numbered so as to give the OH the lowest possible number.

Carboxylic acid component: The root name is based on the longest chain including the carbonyl group. Since the carboxylic acid group is at the end of the chain, it must be C1. The ester suffix for the acid


component is appended after the hydrocarbon suffix minus the "e" : e.g. “-ane” + “-oate” = “-anoate” etc.

Example

Name

methyl ethanoate

Example

Name

propyl propanoate


06 Ketones Keytones are similar to aldehydes as in they have a carbon double bonded to an oxygen, but instead of being bonded to another hydrogen, the carbon is bonded to another carbon atom. These are named by adding “-one” to the end of the name, or by saying keytone at the end.

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