Organic Chemistry Lecture

Alkanes, Alkenes, Alkynes and Hydrocarbon

Jon Jacob Berzelius

In 1809, ___________proposed that compounds derived from living things were organic and that all others were inorganic.

Scientist

The _________ then were certain that organic compounds could be produced only within living systems.

Vital force (Vital Force Theory.)

Living things possessed a _______ as a result of their origin.

Friedrich Wöhler,

a former student of Berzelius, was able to synthesize urea ((NH2 )2CO) when heating an aqueous solution of two inorganic compounds, ammonium chloride and silver cyanate.

Urea

is an organic component of the urine of mammals.

Synthesize Urea

This event disproved the Vital Force theory.

Note:

The weight of evidence was against the Vital Force Theory and it became clear that the only distinguishing characteristic of organic compounds was the presence of the element carbon.

Organic Chemistry

_______then refers to the study of hydrocarbons (compounds of carbon and hydrogen) and their derivatives.

Carbon

An immense diversity of compounds can be formed from the ________element, from the simple to the complex; such as methane, containing one carbon atom, to DNA, containing tens of billions of atoms.

Carbons atom

This is because of the _______ unique ability for bonding, an extent not possible for atoms of any other element.

Carbons atom

___________ can form chains of thousands of atoms or rings of all sizes, which can form branches and cross links.

Organic Chemistry

_______finds importance in various fields; from the chemistry of food, dyes, drugs, paper and inks, paints and plastics, gasoline and rubber tires, etc. It is fundamental to understanding biology and medicine.

Some compounds containing carbon, like carbon monoxide (CO), carbon dioxide (CO2), carbonic acid (H2CO3), and polyatomic ions like bicarbonate (HCO3-) cyanide (CN-), cyanate (CNO-) and carbonate (CO32-)

are considered inorganic substances because their properties resemble those of inorganic compounds.

1. High melting point and boiling point, high densities.

2. Generally soluble in water and rarely soluble in nonpolar solvents.

3. Conduct electric current(electrolyte)

4. Generally nonflammable

5. Ionic bonding

6. Reactions are fast since reactions between ions are fast.

7. Requires very high temperature to decompose.

Inorganic Compounds:

1. Low melting point and boiling point, low densities.

2. Most are not soluble in water but are generally soluble in nonpolar solvents

3. Do not conduct current(nonelectrolyte)

4. Generally flammable to produce CO2 and water.

5. Covalent bonding

6. Reactions are generally slower due to slower breakage of covalent bonds.

7. Decomposes easily when heated.

Organic Compound

Note:

The four covalent bonding positions of the carbon atom can give rise to a wide diversity of compounds with many functions, accounting for the importance of carbon in living things. The following are the steps on how carbon atom meets its FOUR bond requirement:

Molecular formula

______shows the number of each type of atom that is present in the molecule of the compound. Ex. C2H6

Structural Formula

_______shows the details of the bonding present in the molecule, i.e., which atoms are connected to which other atom. Ex. H H H C C H HH

Full or Expanded Structural Formula

______All the atoms and bonds are indicated.

Condensed Structural Formula

an abbreviated form of writing formulas. ∙ Shows no bonds ∙ Shows all carbon-carbon bonds but no carbon-hydrogen bonds. Ex. CH3CH3

Line Structural Formula

uses lines to show the structure of the compound where; ⮚ Carbon atoms are present at the intersection of two or more lines and wherever a line begins or ends. ⮚ Hydrogen atoms bonded to Carbon are not shown. Because carbon always has a valence of four, we mentally supply the correct number of Hydrogens. ⮚ All atoms other than carbon and hydrogen are shown.

Hydrocarbon

_____is a compound that contains only carbon atoms and hydrogen atoms. Thousands of hydrocarbons are known.

Hydrocarbon derivative

______is a compound that contains carbon and hydrogen and one or more additional elements. Additional elements commonly found in hydrocarbon derivatives include O, N, S, P, F, Cl, and Br. Millions of hydrocarbon derivatives are known.

saturated and unsaturated.

Hydrocarbons may be divided into two large classes:

saturated hydrocarbon

_________is a hydrocarbon in which all carbon-carbon bonds are single bonds.

• the simplest type of organic compound.

unsaturated hydrocarbon

_________ is a hydrocarbon in which one or more carbon-carbon multiple bonds (double bonds, triple bonds, or both) are present.

Aromatic Hydrocarbon

________contains a benzene ring. Benzene C6H6 is a functional group characterized by a ring of six carbon atoms, bonded by alternating single and double bonds.

Acyclic and Cyclic

Two categories of saturated hydrocarbons exist,:

Acyclic

term _______means ―not cyclic.‖

Alkane

____single bond

Alkene

_____double bond

Alkyne

______triple bond

Alcohol

Hydroxyl group

Ether

Ether linkage

Thiol

sulfhydryl group

Aldehyde

carbonyl group

Ketone

carbonyl group 2

Carboxylic acid

carboxyl group

Ester

ester group

Amide

amide group

Amine

amino group

Alkane

_______is a saturated hydrocarbon in which the carbon atom arrangement is acyclic. - have a general formula CnH2n + 2 , where n represents the number of C-atoms. This general formula shows a homologous series of carbon atoms.

Alkane

Each number in this series differ from its immediate neighbor by a methylene group, CH2 , which is called a homologous

• they contain single bonds between carbon atoms

• also known as the paraffin series

• nomenclature of these hydrocarbons ends with "-ane"

• the C atoms are saturated with hydrogen atoms

Common name

When relatively few organic compounds were known, chemists arbitrarily named them using what today are called ____________

nonsystematic approach

These common names gave NO information about the structures of the compounds they described. However, as more organic compounds became known, this ___________ to naming compounds became unwieldy.

systematic rules

Today, formal __________ exist for generating names for organic compounds. These rules, which were formulated and are updated periodically by the International Union of Pure and Applied Chemistry (IUPAC), are known as IUPAC rules.

IUPAC naming system

The advantage of the________________ is that it assigns each compound a name that not only identifies it but also enables one to draw its structural formula.

branched-chain alkane, substituent

To name__we must be able to name the branch or branches that are attached to the main carbon chain. These branches are formally called _

Substituent

__________is an atom or group of atoms attached to a chain (or ring) of carbon atoms.

substituent

Note that ________ is a general term that applies to carbon-chain attachments in all organic molecules, not just alkanes.

Alkyl groups

For branched-chain alkanes, the substituents are specifically called ________

Alkyl groups

is the group of atoms that would be obtained by removing a hydrogen atom from an alkane. Nomenclature of these group ends with "yl"

Identify the longest continuous carbon chain (the parent chain), -Number the carbon atoms in the parent chain from the end of the chain nearest a substituent (alkyl group). There always are two ways to number the chain (either from left to right or from right to left). This rule gives the first-encountered alkyl group the lowest possible number. -If only one alkyl group is present, name and locate it (by number), and prefix the number and name to that of the parent carbon chain. two or more of the same kind of alkyl group are present in a molecule, indicate the number with a Greek numerical prefix (di-, tri-, tetra-, penta-, and so forth). In addition, a number specifying the location of each identical group must be included. These position numbers, separated by commas, precede the numerical prefix. Numbers are separated from words by hyphens. -When two kinds of alkyl groups are present on the same carbon chain, number each group separately, and list the names of the alkyl groups in alphabetical order. Follow IUPAC punctuation rules, which include the following: (1) Separate numbers from each other by commas. (2) Separate numbers from letters by hyphens (3) Do not add a hyphen or a space

RULES in IUPAC naming system of branched alkanes:

sec- and tert-, are NOT considered when alphabetizing. The prefixes iso and neo are not hyphenated prefixes and are included when alphabetizing. The following IUPAC name is thus correct:

In IUPAC naming, hyphenated prefixes, such as:

Isomers

______are compounds that have the same molecular formula (that is, the same numbers and kinds of atoms) but different structures.

Isomers

______-are composed of the same collection of atoms, they differ in one or more physical or chemical properties such as color, solubility, or rate of reaction with some reagents hence are always different compounds.

Structural Isomers (Constitutional Isomer)

_____are compounds that have the same molecular formula but different structures. Compounds that differ from each other in connectivity

Combustion Reaction

________ is a chemical reaction between a substance and oxygen (usually from air) that proceeds with the evolution of heat and light (usually as a flame).

Alkanes

_______readily undergo combustion when ignited. When sufficient oxygen is present to support total combustion, carbon dioxide and water are the products. Combustion is a type of oxidation reaction.

Combustion Reaction, Halogenation Reaction, Nitration, Isomerization

4 Reaction of Alkane:

HALOGENATION REACTION

__________is a chemical reaction between a substance and a halogen in which one or more halogen atoms are incorporated into molecules of the substance.

Alkane Halogenation

___________is an example of a substitution reaction, a type of reaction that occurs often in organic chemistry.

Substitution Reaction

is a chemical reaction in which part of a small reacting molecule replaces an atom or a group of atoms on a hydrocarbon or hydrocarbon derivative. The halogens are the elements in Group VIIA of the periodic table: fluorine (F2 ), chlorine (Cl2 ), bromine (Br2 ), and iodine (I2 ).

Alkane

In halogenation of an _________ , is said to undergo fluorination, chlorination, bromination, or iodination, depending on the identity of the halogen reactant.

Chlorination and bromination

_____ and _____ are the two widely used alkane halogenation reactions.

Fluorination reactions

________reactions generally proceed too quickly to be useful, and iodination reactions go too slowly.

Halogenation

usually results in the formation of a mixture of products rather than a single product. More than one product results because more than one hydrogen atom on an alkane can be replaced with halogen atoms.

Nitration

_____alkanes react with nitric acid (HNO3 ) at an elevated temperature to give nitroalkane

Isomerization

_________rearrangement of the structure of the compound to produce isomers. The most important catalysts found for this reaction are aluminum chloride and aluminum bromide.

Catalyst

_______in chemistry, any substance that increases the rate of a reaction without itself being consumed.

Methane, ethane, propane and butane

_______are gases at room temperature. They are used for fuels. pentane to heptadecane are liquids; the higher alkanes are solids at room temperature.

Methane

_____ is the simplest hydrocarbon.

Methane

_____is a greenhouse gas.

Butane

_______ is sold in canisters, for cooking and camping. It is also used as fuel in cigarette lighters.

unprocessed natural gas

______contains 50%-90% methane, 1%-10% ethane, and up to 8% higher-molecular-mass alkanes (predominantly propane and butane). e. Crude petroleum is a complex mixture of hydrocarbons (both cyclic and acyclic) that can be separated into useful fractions through refining.

Alkane

The boiling point and melting point of _______increase with increasing number of C atoms.

Alkane

________ are insoluble in water and in cold H2SO4 but very soluble in organic solvents.

Alkanes

______have densities lower than that of water.

• are inert with many reagents, they do not undergo addition reactions.

Alkanes

______are saturated because they have only single bonds.

Petroleum

Alkanes principal source is

Halogenated hydrocarbons

_______are useful in the dry cleaning industry due to their ability to dissolve dirt and grease.

Haloalkanes

_______known as freons are used as refrigerants but they can damage the ozone layer.

NItroalkanes

______are used as solvents and as intermediates in the preparation of other compounds.

Cycloalkanes

_______is cyclic structure of rearranged straight chain hydrocarbon compounds where the ends meet at a common point forming a ring

Cyloalkane

______named by prefixing cyclo to the open chain alkane having the same number of carbon as a ring

Alkenes

_____is an acyclic unsaturated hydrocarbon that contains one or more carbon to carbon double bonds.

Alkenes

The alkene functional group is C = C group (double bond).

Alkenes

_____Names are derived from the names of alkanes with the same number of C-atoms by replacing suffix ―ane‖ with ―ene‖

Cycloalkenes

______is a cyclic unsaturated hydrocarbon

• general formula of CnH2n - 2

• are isomeric with alkynes

• cyclic alkene is named by prefixing cyclo to the open chain alkene having the same number of carbon as a ring

Alkenes

_____like alkanes, are very flammable. The combustion products, as with any hydrocarbon, are carbon dioxide and water.

Addition reaction

_______is a reaction in which atoms or groups of atoms are added to each carbon atom of a carbon-carbon multiple bond in a hydrocarbon or hydrocarbon derivative.

Hydrogenation Reaction

______is an addition reaction in which hydrogen (H2 ) is incorporated into molecules of an organic compound.

Alkene

_____hydrogenation a hydrogen atom is added to each carbon atom of a double bond. It is accomplished by heating the alkene and H2 in the presence of a catalyst (usually Nickel or Platinum).

halogenation reaction

______is an addition reaction in which a halogen is incorporated into molecules of an organic compound.

halogenation reaction

In alkene halogenation a halogen atom is added to each carbon atom of a double bond. Chlorination (Cl2 ) and bromination (Br2 ) are the two halogenation processes most commonly encountered. No catalyst is needed.

Hydrohalogenation reaction

is an addition reaction in which a hydrogen halide (HCl, HBr, or HI) is incorporated into molecules of an organic compound. -In alkene hydrohalogenation one carbon atom of a double bond receives a halogen atom and the other carbon atom receives a hydrogen atom. Hydrohalogenation reactions require no catalyst.

MARKOVNIKOV'S RULE Vladimir V. Markovnikov

When two isomeric products are possible, one product usually predominates. The dominant product can be predicted by using Markovnikov's rule, named after the Russian chemist Vladimir V. Markovnikov. ________ states that when an unsymmetrical molecule of the form HX adds to an unsymmetrical alkene, the hydrogen atom from the HX becomes attached to the unsaturated carbon atom that already has the most hydrogen atoms.

Markovnikov's rule,

_______the major product in the hydrohalogenation of propene is 2-chloropropane. (Markovnikov's rule : the hydrogen atom from the HX becomes attached carbon atom with double bond that already has the most hydrogen atoms.)

Hydration Reaction

is an addition reaction in which H2O is incorporated into molecules of an organic compound. In alkene hydration one carbon atom of a double bond receives a hydrogen atom and the other carbon atom receives an —OH group. Alkene hydration requires a small amount of H2SO4 (sulfuric acid) as a catalyst.

When two isomeric products are possible, one product usually predominates. The dominant product can be predicted by using Markovnikov's rule.