Organic Chemistry Saturated & Unsaturated Hydrocarbons

Home , Halogenation, Unsaturated hydrocarbon

Organic Chemistry Saturated & Unsaturated Hydrocarbons BIOB111 CHEMISTRY & BIOCHEMISTRY

| Courtesy of SAMPORHELP | Downloaded fromSession https://www.thebigvault.net 8 Key concepts: session 8

From this session you are expected to develop an understanding of the following concepts:

Concept 1: Solubility of hydrocarbons in H2O

Concept 2: Creation of CFC compounds

Concept 3: Alkyl groups

Concept 4: Reactivity of saturated vs unsaturated hydrocarbons

Concept 5: Alkanes vs alkenes vs alkynes

Concept 6: Conversion between the hydrocarbon functional groups (alkane, alkene and alkyne)

Concept 7: Bromination reactions

Concept 8: Properties of benzene

Concept 9: Hydration reactions

Concept 10: Identifying primary, secondary and tertiary alcohols

These concepts are covered in the Conceptual multiple choice questions of tutorial 8 | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Session Overview Part 1: Exploring saturated hydrocarbon compounds • Saturated vs unsaturated hydrocarbon compounds • Chemical properties of alkanes • Alkyl groups are derived from alkanes

Part 2: Exploring unsaturated hydrocarbon compounds • Chemical properties of alkenes • Bromination reactions • Chemical properties of alkynes • Chemical properties of benzene

Part 3: The alcohol function group • Hydrocarbon derivatives • Chemical properties of alcohols

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Hydrocarbon derivatives

Life on earth would not exist without organic compounds that contain carbon atoms

• Our genetic material (DNA) contains many carbon atoms

• Our bodies rely on the organic compounds below to function:

– Proteins are made up of amino acids

– Lipids are often made up of fatty acids (long hydrocarbons) and glycerol

– Carbohydrates are made up of one or more monosaccharide (sugar) units

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Saturated vs unsaturated hydrocarbon compounds Hydrocarbon compounds: The most basic organic compounds are hydrocarbons

– Hydrocarbons contain only carbon and hydrogen atoms

– Hydrocarbons compounds are created in nature and can be synthesised in the laboratory

Structures of Hydrocarbon compounds Each line connecting the atoms below represents a covalent bond (2 electrons shared between the two | Courtesy of SAMPORHELP | connected atoms) Downloaded from https://www.thebigvault.net Saturated vs unsaturated hydrocarbon compounds

HYDROCARBONS BELONG TO ONE OF THREE FUNCTIONAL GROUPS

Type Type

Type ALKANE ALKENE Example

Definition Definition ALKYNE CONTAIN ONLY CONTAIN ONE CONTAIN ONE OR Example Definition Example SINGLE CARBON MORE DOUBLE OR MORE TO CARBON CARBON TO TRIPLE CARBON BONDS CARBON BONDS TO CARBON BONDS

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Saturated vs unsaturated hydrocarbon compounds ORGANIC COMPOUNDS THAT CONTAIN CARBON Definition AND HYDROGEN ATOMS HYDROCARBONS Type REACTIVE SATURATED Due to HYDROCARBON Type Are Are DOUBLE AND TRIPLE CARBON TO CARBON UNREACTIVE UNSATURATED BONDS CAN EASILY BE Definition Due to HYDROCARBON BROKEN IN A CHEMICAL REACTION Definition LARGE AMOUNT OF ENERGY NEEDED TO CONTAIN ONE OR MORE DOUBLE OR CONTAIN ONLY BREAK THE SINGLE TRIPLE CARBON TO CARBON BOND, SINGLE CARBON TO BONDS PRESENT ALSO CONTAIN ONE OR MORE

| Courtesy ofCARBON SAMPORHELP | BONDS SINGLE CARBON TO CARBON BONDS Downloaded from https://www.thebigvault.net Saturated vs unsaturated hydrocarbon compounds

Saturated hydrocarbons Unsaturated hydrocarbons • Contain only single carbon to • Contain one or more double or carbon bonds triple carbon to carbon bond – Are also likely to contain one or • Functional groups: Alkane more single carbon to carbon bonds • Unreactive and stable • Functional groups: Alkene, alkyne – Due to the large amount of energy • Reactive and unstable (compared needed to break the existing chemical to saturated hydrocarbons) bonds – Due to the small amount of energy required to break the double or triple carbon to carbon bonds present

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Saturated vs unsaturated hydrocarbon compounds Saturated Hydrocarbons – Saturated hydrocarbons have only single carbon to carbon bonds

– The carbon atoms in saturated hydrocarbons form bonds to the maximum amount of hydrogen atoms possible • These compounds are saturated with hydrogen atoms

– Include alkanes (straight chains) & cycloalkanes (carbon rings)

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Saturated vs unsaturated hydrocarbon compounds Unsaturated Hydrocarbons – Unsaturated hydrocarbons have one or more double or triple carbon to carbon bond(s) • Will also contain single carbon to carbon bonds

– The carbon atoms in unsaturated hydrocarbons form bonds to less than the maximum amount of hydrogen atoms possible • These compounds are not saturated with hydrogen atoms (unsaturated) – Due to the presence of double or triple carbon to carbon bonds

– Include Alkenes (straight chains) & Cycloalkenes (carbon rings)

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Saturated vs unsaturated hydrocarbon compounds

Number of Carbon Atoms Prefix Alkane Alkene Alkyne 1 Meth- Methane - - 2 Eth- Ethane Ethene Ethyne 3 Prop- Propane Propene Propyne 4 But- Butane Butene Butyne 5 Pent- Pentane Pentene Pentyne 6 Hex- Hexane Hexene Hexyne 7 Hept- Heptane Heptene Heptyne 8 Oct- Octane Octene Octyne 9 Non- Nonane Nonene Nonyne 10 Dec- Decane Decene Decyne

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Propane is an alkane: Chemical properties of alkanes Used as a fuel for cars (LPG gas) Functional Group: Alkane

Distinguishing characteristic: Alkane compounds contain only single carbon to carbon bonds

Naming convention: Alkane compounds have –ane at the end of their name e.g. propane

Example compound:

| Courtesy of SAMPORHELP | Propane Downloaded from https://www.thebigvault.net Chemical properties of alkanes

HYDROCARBONS BELONG TO ONE OF THREE FUNCTIONAL GROUPS

Type Type

Type ALKANE ALKENE Example

Definition Definition ALKYNE CONTAIN ONLY CONTAIN ONE CONTAIN ONE OR Example Definition Example SINGLE CARBON MORE DOUBLE OR MORE TO CARBON CARBON TO TRIPLE CARBON BONDS CARBON BONDS TO CARBON BONDS

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkanes Alkanes are non-polar compounds

– Alkanes contain only carbon and hydrogen atoms which are connected via non-polar covalent bonds (equal electron sharing)

H2O is a polar compound

– H2O contains polar covalent bonds where the shared electrons are more attracted to the oxygen atom than the hydrogen atoms

• Compounds must be polar to dissolve in H2O

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkanes

Will an alkane compound (such as propane) dissolve in H2O?

– Non-polar alkanes do not dissolve in polar H2O

– Alkanes are insoluble in H2O

– The non-polar alkane will only dissolve in Propane non-polar solvents such as chloroform

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkanes Combustion – Combustion reactions are exothermic reactions that release heat

– Alkanes burn in the presence of oxygen producing CO2, H2O and heat via combustion reactions

– Example: combustion of methane

CH4 + 2O2 → CO2 + 2H2O + Energy – All combustion reactions are redox reactions where one reactant is oxidised and one is reduced • Oxygen is always reduced

| Courtesy of SAMPORHELP | in redox reactions https://www.freeimages.com/photo/fire-camp-1174281 Downloaded from https://www.thebigvault.net Chemical properties of alkanes Halogenation – Halogenation reactions involve an alkane reacting with

a halogen molecule such as Cl2 or F2

– The end result of a halogenation reaction: • Substitution of one of the alkane’s hydrogen atoms with a halogen atom, producing a halogenated alkane

Methane Halogen Halogenated molecule alkane | Courtesy of SAMPORHELP | Stoker 2014, p368-70 Downloaded from https://www.thebigvault.net Halogenation • During a halogenation reaction the alkane’s hydrogen atom is replaced by a single halogen atom, producing a halogenated alkane • The lost hydrogen atom forms a compound with the other halogen atom (from the halogen molecule), in this case creating the strong acid HCl

H Large energy H input H C H + Cl Cl H C Cl + H Cl Halogen H molecule H Methane Halogenated alkane • Additional hydrogen atoms can be substituted in the halogenated alkane by performing

| Courtesy of additionalSAMPORHELP | halogenation reactions Downloaded from https://www.thebigvault.net Chemical properties of alkanes

Halogenated alkane

H Energy HCl product input Energy input H C H + Cl Cl Halogen H molecule Methane Reactant Reactant

Animation of a halogenation reaction | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkanes

Chlorofluorocarbons (CFCs) – Synthetic organic compounds that were developed to be used as refrigerants • Refrigerants can be used to heat a pump that powers refrigeration

– The 2 most commonly used CFCs were Freon-11 and Freon-12 • CFCs destroyed a significant amount of the ozone layer in the stratosphere until banned

| Courtesy of SAMPORHELP | Stoker 2014, p373 Downloaded from https://www.thebigvault.net How many halogenation reactions would it take to

convert methane (CH4) into a halogenated alkane that contains three fluorine atoms?

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Alkyl groups are derived from alkanes Alkyl Groups – Once an alkane loses one of its hydrogen atoms it becomes an alkyl group

Alkane loses a hydrogen atom

Alkane: methane Alkyl group: methyl

• Naming: replace the -ane with -yl at the end of the name – Methane becomes methyl

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Alkyl groups are derived from alkanes Alkyl Groups – Once an alkane loses one of its hydrogen atoms it becomes an alkyl group

– Alkyl groups can attach to an atom or compound by forming a covalent bond

Alkyl group: Methyl group methyl branching off a 5 carbon chain

Methyl R represents an attachment point to another atom or Group compound | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Alkyl groups: derived from alkanes

After methane loses a hydrogen = methyl group R—CH3

After ethane loses a hydrogen = ethyl group R—CH2—CH3

After propane loses a hydrogen = propyl group R—CH2—CH2—CH3

Ethyl group branching off a 5 carbon chain Ethyl Group

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Identify the name and position of the alkyl group in the compound below

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Attempt Socrative questions: 1 to 3

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City name followed by 1 or 2 (e.g. PERTH1)

1 for 1st session of the week and 2 for 2nd session of the week

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Part 1: Exploring saturated hydrocarbon compounds • Saturated vs unsaturated hydrocarbon compounds – Saturated hydrocarbons contain only single carbon to carbon bonds and contain the maximum number of hydrogen atoms attached to the carbon atoms – Alkanes and cycloalkane are saturated hydrocarbons – Unsaturated hydrocarbons contain one or more double or triple carbon to carbon bonds, as well as other single carbon to carbon bonds – Unsaturated hydrocarbons contain less than the maximum number of hydrogen atoms attached to the carbon atoms, due to the presence of double or triple carbon to carbon bonds – Alkenes and cycloalkenes are unsaturated hydrocarbons

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Part 1: Exploring saturated hydrocarbon compounds • Chemical properties of alkanes

– Alkanes are non-polar compounds that do not dissolve in H2O (insoluble in H2O) – Alkanes burn in oxygen in combustion reactions (type of redox reaction)

– Alkanes can react with halogen molecules (e.g. Cl2) to replace one hydrogen at a time with a halogen atom via a halogenation reaction

• Alkyl groups are derived from alkanes – Once an alkane loses one of its hydrogen atoms it becomes an alkyl group – Alkyl groups can attach to an atom or compound by forming a covalent bond – Methane becomes a methyl group by losing a hydrogen atom

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Part 2: Exploring unsaturated hydrocarbon compounds • Chemical properties of alkenes • Bromination reactions • Chemical properties of alkynes • Chemical properties of benzene

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes

Functional Group: Alkene Distinguishing characteristic: Alkene compounds contain one or more double carbon to carbon bond(s), and will also likely contain some single carbon to carbon bonds

Naming convention: Alkene compounds have -ene at the end of their name e.g. propene

Example compound:

| Courtesy of SAMPORHELP | Propene Downloaded from https://www.thebigvault.net Chemical properties of alkenes

HYDROCARBONS BELONG TO ONE OF THREE FUNCTIONAL GROUPS

Type Type

Type ALKANE ALKENE Example

Definition Definition ALKYNE CONTAIN ONLY CONTAIN ONE CONTAIN ONE OR Example Definition Example SINGLE CARBON MORE DOUBLE OR MORE TO CARBON CARBON TO TRIPLE CARBON BONDS CARBON BONDS TO CARBON BONDS

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes Stereoisomers are a group of two compounds that are very similar: • The group of compounds has the same number of each type of atom present and the same chemical bonding pattern • Each of the two stereoisomer compounds are arranged differently in space

– The two different variations of the stereoisomer compounds have different chemical properties

– Example:

• cis stereoisomer = both large CH3 groups are on the same side of the carbon to carbon double bond

• Trans stereoisomer = The large CH3 groups are on different sides of the carbon to carbon double bond cis = same trans = different The stereoisomer pair to the right are alkenes | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes • Unsaturated hydrocarbons (such as alkenes and alkynes) are more reactive than saturated hydrocarbons (such as alkanes)

– Alkanes contain only single carbon to carbon bonds, which require significant input energy to break • Difficult to replace hydrogen atoms attached to carbons with other atoms (e.g. halogens Cl, F) – Alkanes stable and unreactive

Each line represents a single covalent bond that requires significant input energy to break

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes • Unsaturated hydrocarbons (such as alkenes and alkynes) are more reactive than saturated hydrocarbons (such as alkanes)

– Alkenes and alkynes have double and triple carbon to carbon bonds, respectively

– A double or triple carbon to carbon bond can be broken with a smaller amount of input energy than single carbon to carbon bond

– Once a double or triple carbon to carbon bond has been broken: • Other atoms can bond to the carbon atoms that were previously part of the multiple carbon to carbon bond – Carbon must have 4 covalent bonds at all times to be stable

Multiple carbon to carbon bonds which can be broken with a small amount of input energy

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes

Animation of the reactivity of an alkene

H H Energy H Energy input input H C C C + Cl Cl H H

Once the double carbon to carbon bond is broken the two chlorine atoms are incorporated into the compound, which allows each carbon atom to have 4 covalent bonds

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes • Alkenes can take part in addition reactions:

• Breaking a multiple carbon to carbon bond creates new positions where carbon atoms can form covalent bonds to other atoms

Addition Reaction Reactants Products

HYDROGENATION Alkene + H2 Alkane

HALOGENATION Alkene + Cl2 or Br2 Halogenated alkane

HYDRATION Alkene + H2O Alcohol

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes Hydrogenation reaction

Addition of a H2 molecule into an alkene: • Replaces the double carbon to carbon bond with two new covalent bonds between the carbon atoms and the added hydrogen atoms

– End result: the alkene is converted to an alkane

• The carbon atoms that form the new bonds with the added hydrogen atoms were previously part of the double carbon to carbon bond

Propene (alkene) Hydrogen Propane (alkane) molecule

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes Animation of a hydrogenation reaction where an alkene is converted into an alkane

H H Energy H Energy input input H C C C + H H H H

Once the double carbon to carbon bond is broken the two hydrogen atoms are incorporated into the compound, which allows each carbon atom to have 4 covalent bonds

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes Hydration reaction

Addition of a H2O molecule into an alkene: • Replaces the double carbon to carbon bond with two new covalent bonds between one carbon atom and H, a second carbon atoms and an OH group

– End result: the alkene is converted to an alcohol (contains the alcohol functional group)

• The carbon atoms that form the new bonds with the H and OH were previously part of the double carbon to carbon bond Propene (alkene) water Propanol (alcohol) molecule

Alcohol functional group | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes Animation of a hydration reaction where an alkene is converted into an alcohol

H H Energy H Energy input input H C C C + OHH2OH H H Alcohol functional group

Once the double carbon to carbon bond is broken the OH group and a hydrogen atom are incorporated into the compound, which allows each carbon atom to have 4

| Courtesy of SAMPORHELP | covalent bonds Downloaded from https://www.thebigvault.net Chemical properties of alkenes Halogenation reaction

Addition of a halogen molecule (e.g. Cl2) into an alkene: • Replaces the double carbon to carbon bond with two new covalent bonds between the carbon atoms and the added halogen atoms

– End result: the alkene is converted to a halogenated alkane

• The carbon atoms that form the new bonds with the added halogen atoms were previously part of the double carbon to carbon bond • Each halogenation reaction with an alkene adds two halogen atoms at a time

Propene (alkene) Halogen Halogenated alkane molecule

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkenes Animation of a halogenation reaction where an alkene is converted into a halogenated alkane

H H Energy H Energy input input H C C C + Cl Cl H H

Once the double carbon to carbon bond is broken the two chlorine atoms are incorporated into the compound, which allows each carbon atom to have 4 covalent bonds

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net • Bromine is a halogen (Br2) that can readily be added into an alkene via a halogenation reaction

Halogenated alkane Propene (alkene) Halogen molecule

Reactive

• A large amount of input energy is needed to add bromine atoms into an alkane one at a time via a halogenation reaction, so the reaction occurs less often

Propane (alkane) Halogen Halogenated alkane molecule Large energy input

| Courtesy of SAMPORHELP | Less reactive Downloaded from https://www.thebigvault.net Bromination reactions • A Bromination test is used to determine whether a solution contains a dissolved alkane or alkene

– When in solution, bromine is red

– When bromine is incorporated into a compound the solution becomes colourless

Once all of the bromine is The red colour shows that incorporated into a compound, bromine is in the solution | Courtesy of SAMPORHELP | the solution is colourless Stoker 2014, p399 Downloaded from https://www.thebigvault.net Bromination reactions

What will happen when bromine is added to an alkane solution?

– When bromine (Br2) is added to an alkane solution, the red color of bromine persists

• Br2 is not incorporated into the alkane compound • No chemical reaction occurs due to large amount of energy needed to begin the reaction

The red bromine is not incorporated into the alkane compound

The red colour remains as bromine has not been incorporated into a | Courtesy of SAMPORHELP | compound Stoker 2014, p399 Downloaded from https://www.thebigvault.net Bromination reactions

What will happen when bromine is added to an alkene solution?

– When bromine (Br2) is added to an alkene or alkyne solution, the red color of bromine disappears quickly

• Br2 is readily incorporated into the alkene compound, which becomes a halogenated alkane via a halogenation reaction

Bromine is readily incorporated into the alkene compound

Once all of the bromine is incorporated into a compound, | Courtesy of SAMPORHELP | the solutions is colourless Stoker 2014, p399 Downloaded from https://www.thebigvault.net Chemical properties of alkynes

Functional Group: Alkyne Distinguishing characteristic: Alkyne compounds contain one or more triple carbon to carbon bond(s), and will also likely contain some single carbon to carbon bonds

Naming convention: Alkyne compounds have –yne at the end of their name e.g. propyne

Example compound:

Propyne | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkynes

HYDROCARBONS WHICH CONTAIN ONLY CARBON AND HYDROGEN ATOMS BELONG TO ONE OF THREE FUNCTIONAL GROUPS

Type Type

Type ALKANE ALKENE Example

Definition Definition ALKYNE CONTAIN ONLY CONTAIN ONE CONTAIN ONE OR Example Definition Example SINGLE CARBON MORE DOUBLE OR MORE TO CARBON CARBON TO TRIPLE CARBON BONDS CARBON BONDS TO CARBON BONDS

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkynes • Alkynes behave similarly to alkenes in chemical reactions

– Both have multiple carbon to carbon bonds which can be broken with a small energy input

• Alkynes can participate in many of the same chemical reactions as alkenes:

– Hydrogenation • Adding two hydrogen atoms

– Hydration

• Adding H2O, which creates an alcohol group

– Halogenation reactions

| Courtesy of SAMPORHELP | • Adding two halogen atoms Downloaded from https://www.thebigvault.net Chemical properties of alkynes

Which addition reaction could be used to convert and alkyne into an alkane? – How many of these addition reactions would be required?

• Two hydrogenation reactions are required to convert an alkyne into an alkane – Each hydrogenation reaction adds two hydrogen atoms to the compound

+ 2 hydrogen + 2 hydrogen atoms atoms Hydrogenation Hydrogenation

Propyne (alkyne) Propene (alkene) Propane (alkane) | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alkynes Animation of the two hydrogenation reactions required to convert an alkyne into an alkane

Energy H Energy Energy input input H C C inputC H + H H H

Once the doubletriple carbon carbon to to carbon carbon bond bond is isbroken, broken, two two hydrogen atoms are incorporated into the compound, which allows each carbon atom to have 4 covalent bonds

| Courtesy of SAMPORHELPThe alkynealkene | has been converted into an alkenealkane Downloaded from https://www.thebigvault.net Key concept: bonding arrangements of hydrocarbons Are saturated or unsaturated hydrocarbons more reactive?

What types of chemical reactions do the reactive hydrocarbons participate in? What allows the reactive hydrocarbons to participate in these reactions?

How is an alkyne converted to alkane? Does the alkyne compound become more or less stable

| Courtesy of SAMPORHELP | through the conversion to an alkane? Why? Downloaded from https://www.thebigvault.net Attempt Socrative questions: 4 to 8

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| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Aromatic compound: Chemical properties of benzene Benzene is toxic to liver cells (can cause liver cell death) • Aromatic hydrocarbons contain the benzene ring

• Benzene is a unique compound due to the behaviour of its carbon to carbon bonds

Representations of benzene:

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of benzene • When benzene was discovered scientists were puzzled – Benezene had multiple double carbon to carbon bonds but was stable • Benzene behaved more like an alkane than an alkene or alkyne

• Benzene continually switches between two forms where the positions of the double and single carbon to carbon bonds alternate – The two forms of benzene are called resonance structures

| Courtesy of SAMPORHELP | Resonance structure 1 Resonance structure 2 Downloaded from https://www.thebigvault.net Chemical properties of benzene

Animation of the benzene ring switching between it’s resonance structures

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of benzene In the benzene ring: – Every carbon atom is attached to two other carbon atoms by at least one carbon to carbon bond

– 3 extra carbon to carbon bonds in the benzene ring are formed by 6 electrons (2 electrons for each bond) • The extra bonds alternate their positions (see the resonance structures below)

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of benzene In the benzene ring:

• The 6 electrons within the three extra carbon to carbon bonds are equally shared between all 6 carbons in the ring, as the extra bonds continually change position

– The extra carbon to carbon bonds changing position makes it difficult to break them via addition reactions, which makes benzene very stable

– Benzene is much more stable than other unsaturated hydrocarbons, which have static multiple carbon to carbon bonds like alkenes and alkynes

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Key concept: hydrocarbon functional groups How is benzene different to other hydrocarbons such as alkanes, alkenes and alkynes?

What are resonance structures of benzene and how do they explain the stability of benzene?

Would it be easier to break a double carbon to carbon bond within an alkene or in benzene? Justify your answer.

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| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Part 2: Exploring unsaturated hydrocarbon compounds • Chemical properties of alkenes – Alkenes contain a double carbon to carbon bond, which makes the alkene compound more reactive than an alkane compound – The double carbon to carbon bond in an alkene can be broken with a small energy input – Once a double carbon to carbon bond has been broken, other atoms can bond to the carbon atoms (that were previously part of the multiple carbon to carbon bond) to ensure that each carbon forms 4 covalent bonds – Hydrogenation reactions involve breaking the double bond within an alkene compound and replacing the double bond with two new bonds to two hydrogen atoms • Hydrogenation reactions convert alkenes into alkanes – Hydration reactions involve breaking the double bond within an alkene compound and replacing the double bond with two new bonds to one hydrogen atom and one OH group • Hydration reactions convert alkenes into alcohols – Halogenation reactions involve breaking the double bond within an alkene compound and replacing the double bond with two new bonds to two halogen atoms (e.g. chlorine or fluorine) • Halogenation reactions convert alkenes into halogenated alkanes | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Part 2: Exploring unsaturated hydrocarbon compounds • Bromination reactions – Bromine readily reacts with an alkene solution to be incorporated into a new compound, so the red bromine solution becomes colourless as the bromine is taken up into the compound – Bromine does not react readily with an alkane solution, so the red bromine solution remains red

• Chemical properties of alkynes – Alkynes behave similarly to alkenes in chemical reactions – Both alkynes and alkenes have multiple carbon to carbon bonds which can be broken with a small amount of input energy – Alkynes can participate in hydrogenation, hydration and halogenation reactions (just like alkenes) to replace multiple carbon to carbon bonds with new bonds to other atoms | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Part 2: Exploring unsaturated hydrocarbon compounds • Chemical properties of benzene – Benzene continually switches between two forms, called resonance structures, where the positions of the double and single carbon to carbon bonds alternate – Within benzene, the 6 electrons in the three extra carbon to carbon bonds are equally shared by all 6 carbons in the ring, as the bonds continually change position – The movement of the double carbon to carbon bonds within benzene makes it difficult to break the bonds via addition reactions, which makes benzene very stable

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Part 3: The alcohol function group • Hydrocarbon derivatives • Chemical properties of alcohols

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Hydrocarbon derivatives

Hydrocarbon derivatives are: • Hydrocarbon compounds that contain atoms such as oxygen, nitrogen, fluorine or chlorine as well as carbon and hydrogen atoms

– The location within the hydrocarbon derivative that has atoms other than just carbon and hydrogen is where the functional group is located

Ethanol: present in alcoholic beverages

Alcohol

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Hydrocarbon derivatives

What are functional groups? – A functional group is a group of atoms within a compound that provides chemical reactivity

• The functional group is usually the part of the compound that is involved in chemical reactions

• All compounds with a particular functional group will behave similarly in chemical reactions

– To find a functional group within a compound, look for atoms other than just carbon and hydrogen atoms

Ethanol: present in alcoholic beverages

Alcohol

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alcohols

Functional Group: Alcohol Functional group formula: The alcohol functional group is also R OH known as the hydroxyl group

Naming convention: Alcohol compounds have –ol at the end of the name e.g. ethanol

Example compound: The alcohol functional group is located at the end of a compound (or a branch point), as it contains one R-group

| Courtesy of SAMPORHELP | Propanol Downloaded from https://www.thebigvault.net Alcohol Type TERTIARY (3°) Type Functional group ALCOHOL Definition PRIMARY (1°) ALCOHOL Type THE CARBON BONDED Example Definition SECONDARY (2°) TO THE ALCOHOL ALCOHOL FUNCTIONAL GROUP IS THE CARBON BONDED BONDED TO THREE Definition TO THE ALCOHOL OTHER CARBON ATOMS FUNCTIONAL GROUP IS BONDED TO ONE THE CARBON BONDED OTHER CARBON TO THE ALCOHOL Example ATOM FUNCTIONAL GROUP IS BONDED TO TWO OTHER CARBON ATOMS Example | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alcohols

How to work out whether an alcohol is 1°, 2° or 3°:

– Step 1: Identify the carbon that is directly bonded to the alcohol functional group

– Step 2: Count the number of carbon atoms attached to the carbon identified in step 1

The compound has two carbons attached to the carbon bonded to the alcohol functional group = – Step 3: The number of attached carbons identified in step 2 secondary alcohol specifies whether it is a primary, secondary or tertiary alcohol

• 1 attached carbon = 1° Alcohol • 2 attached carbon = 2° Alcohol | Courtesy of SAMPORHELP |• 3 attached carbon = 3° Alcohol Downloaded from https://www.thebigvault.net Classify the following compounds as either a 1°, 2° or 3° alcohols:

1. 3.

2. 4.

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Chemical properties of alcohols Combustion – Combustion reactions are exothermic reactions that release heat

– Alcohols burn in the presence of oxygen producing CO2, H2O and heat via combustion reactions

– Example: combustion of ethanol

C2H6O + 3O2 → 2CO2 + 3H2O + Energy

– All combustion reactions are redox reactions where one reactant is oxidised and one is reduced • Oxygen is always reduced in redox reactions

| Courtesy of SAMPORHELP | https://www.freeimages.com/photo/hell-of-a-drink-1218762 Downloaded from https://www.thebigvault.net Chemical properties of alcohols

Dehydration

(removal of H2O)

Alcohol compound Alkene compound + H2O

Hydration

| Courtesy of SAMPORHELP | (addition of H2O) Downloaded from https://www.thebigvault.net Chemical properties of alkenes Hydration reaction

Addition of a H2O molecule into an alkene: • Replaces the double carbon to carbon bond with two new covalent bonds between the carbon atoms and a H and an OH

– End result: the alkene is converted to an alcohol (contains the alcohol functional group)

• The carbon atoms that form the new bonds with the H and OH were previously part of the double carbon to carbon bond Propene (alkene) water Propanol (alcohol) molecule

H H Energy H Energy input input H C C C + OHH2OH H H Alcohol functional group

Once the double carbon to carbon bond is broken the OH group and a hydrogen atom are incorporated into the compound, which allows each carbon atom to have 4

| Courtesy of SAMPORHELP | covalent bonds Downloaded from https://www.thebigvault.net Chemical properties of alcohols Dehydration reaction:

Removal of a H2O molecule from an alcohol: • The bonds to the OH and H within the compound are broken, allowing an extra carbon to carbon bond to form, which creates a double carbon to carbon bond

– End result: the alcohol is converted into an alkene

• The carbon atoms that lost the bonds to H and OH are the carbon atoms that form the double carbon to carbon bond

• The OH and H that are released from the compound come together to form a H2O molecule

Propanol (alcohol) Propene (alkene) water molecule

Alcohol | Courtesy of SAMPORHELP | functional group Downloaded from https://www.thebigvault.net Chemical properties of alcohols Animation of a dehydration reaction where an alcohol is converted into an alkene H H H H C C C + H2O H OH H H Alcohol functional group

Once the bonds connecting OH and H to the carbon atoms

break, the OH and H come together to form H2O and the carbon atoms form an additional carbon to carbon bond,

| Courtesy of SAMPORHELP | which allows each carbon atom to have 4 covalent bonds Downloaded from https://www.thebigvault.net Attempt Socrative questions: 11 and 12

Google Socrative and go to the student login

Room name:

City name followed by 1 or 2 (e.g. PERTH1)

1 for 1st session of the week and 2 for 2nd session of the week

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Part 3: The alcohol function group • Hydrocarbon derivatives – Hydrocarbon derivatives are compounds that contain atoms such as oxygen, nitrogen, fluorine or chlorine as well as carbon and hydrogen atoms

• Chemical properties of alcohols – The alcohol functional group is located at the end of a compound (or a branch point), as it contains one R-group – The number of carbons attached to the carbon that is bonded to the alcohol group specifies whether the alcohol is primary, secondary or tertiary: • 1 attached carbon = 1° Alcohol • 2 attached carbon = 2° Alcohol • 3 attached carbon = 3° Alcohol – Alcohols burn in oxygen via combustion reactions (a type of redox reaction) – Hydration reactions involve breaking the double bond within an alkene compound and replacing the double bond with new bonds to one hydrogen atom and one OH group • Hydration reactions convert alkenes into alcohols

– Dehydration reactions involve the removal of a H2O molecule from an alcohol, where the bonds to the OH and H that make up H2O are replaced by a extra carbon to carbon bond (creates a double carbon to carbon double bond in the compound) • Dehydration reactions convert alcohols into alkenes

| Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net Readings & Resources • Stoker, HS 2014, General, Organic and Biological Chemistry, 7th edn, Brooks/Cole, Cengage Learning, Belmont, CA. • Stoker, HS 2004, General, Organic and Biological Chemistry, 3rd edn, Houghton Mifflin, Boston, MA. • Timberlake, KC 2014, General, organic, and biological chemistry: structures of life, 4th edn, Pearson, Boston, MA. • Alberts, B, Johnson, A, Lewis, J, Raff, M, Roberts, K & Walter P 2008, Molecular biology of the cell, 5th edn, Garland Science, New York. • Berg, JM, Tymoczko, JL & Stryer, L 2012, Biochemistry, 7th edn, W.H. Freeman, New York. • Dominiczak, MH 2007, Flesh and bones of metabolism, Elsevier Mosby, Edinburgh. • Tortora, GJ & Derrickson, B 2014, Principles of Anatomy and Physiology, 14th edn, John Wiley & Sons, Hoboken, NJ. • Tortora, GJ & Grabowski, SR 2003, Principles of Anatomy and Physiology, 10th edn, John Wiley & Sons, New York, NY. | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net | Courtesy of SAMPORHELP | Downloaded from https://www.thebigvault.net