CORE ORGANIC

OCR A A LEVEL CHEMISTRY

What is the functional group of an alcohol?

\-OH

What is the general formula for alcohols?

CₙH₂ₙ₋₁OH

How do you name alcohols?

hydroxy-, -ol

What kind of intermolecular forces do alcohols have?

hydrogen bonding

Why do alcohols have hydrogen bonding?

the OH bond is highly electronegative

How do alcohols’ melting and boiling point compare to hydrocarbons of similar carbon chain lengths?

higher melting/boiling points

Why do alcohols have higher melting and boiling points as hydrocarbons of similar chain length?

hydrogen bonding is stronger than London forces

Are alcohols soluble in water?

soluble in short chains - hydrogen bonding with water

insoluble in long chain - non-polarity of CH bond takes precedence

What is a primary alcohol?

the C with the -OH group is bonded to one other Carbon atom

What is a secondary alcohol?

the C with the -OH group is bonded to 2 other carbon atoms

What is a tertiary alcohol?

the C with the -OH group is bonded to 3 other carbons

What forms when you partially oxidise a primary alcohol?

aldehyde -CHO

What conditions are needed to partially oxidise a primary alcohol?

* dilute H₂SO₄
* potassium dichromate(VI) / Cr₂Kr₂O₇
* distill product as it’s produced
* gentle heating

What is the equation for the partial oxidation of ethanol?

CH₃CH₂OH + \[O\] → CH₃CHO + H₂O

What forms when you fully oxidise a primary alcohol?

carboxylic acid, -COOH

What conditions are needed to fully oxidise a primary alcohol?

* conc. H₂SO₄
* K₂Cr₂O₇
* reflux
* strong heat

What is the equation for the full oxidation for ethanol?

CH₃CH₂OH + 2\[O\] → CH₃COOH + H₂O

What forms when you oxidise a secondary alcohol?

ketone

What conditions are needed to fully oxidise a secondary alcohol?

* conc. H₂SO₄
* potassium dichromate (VI)
* strong heating

What is the equation for the oxidation of propan-2-ol?

CH₃CH(OH)CH₃ + \[O\] → CH₃COCH₃ + H₂O

Is it possible to oxidise a tertiary alcohol?

no

What is a dehydration reaction?

a reaction in which water is lost to form an organic compound

What are the products of a dehydration reaction with alcohol?

alkene and water

What conditions are required for the dehydration of alcohols?

* conc. H₂SO₄
* conc. H₃PO₄
* 170°C

What products are formed in halide substituition with alcohol?

haloalkane and water

What conditions are needed for an alcohol to form a halogenoalkane?

* NaX
* H₂SO₄
* heated under reflux

What are haloalkanes?

saturated organic compunds that contain carbon atoms and at least one halogen atom

Are haloalkanes soluble in water?

no

Why aren’t haloalkanes soluble in water?

C-H bonds are non-polar, not compensated for enough by C-X bond polarity

Do haloalkanes have a polar bond?

Yes, halogen has a higher electronegativity than C

Which intermolecular forces do haloalkanes have?

permanent dipole-dipole, London forces

What causes an increase in the boiling point of a haloalkane?

* increased carbon chain length
* halogen further down group 7

How would the mass of a haloalkane compare with the mass of an alkane of the same chain length?

greater (halogen mass > carbon mass)

What is the most important factor in determining halogen reactivity?

strength of the carbon-halogen bond

What would bond polarity suggest the order of reactivity of haloalkanes would be?

C-F would be the most reactive (most polar)

What does bond enthalpy suggest the order of reactivity of haloalkanes would be?

C-I would be the most reactive (lowest bond enthalpy)

What is a nucleophile?

electron pair donor

What are some examples of nucleophiles?

\:OH⁻, :CN⁻, :NH₃⁻, :Cl⁻

What is nucleophilic substituition?

a nucleophile donates a lone pair of electrons to a C⁶⁺ atom and the ⁶⁻ atom is replaced by the nucleophile

What is hydrolysis?

reaction in which water is a reactant

Which reactant often produces hydroxide ions for hydrolysis?

water/H₂O

What fission does water undergo to produce OH⁻?

heterolytic

What are CFCs?

chlorofluorocarbons (haloalkanes containing only C, Cl, F)

What is the problem with CFCs?

catalyse the breakdown of ozone in the atmosphere (via free radical substituition)

What is the main function of the ozone layer?

provides protection from harmful UV rays

Does ozone protect in all layers of the atmosphere?

no, in the troposphere it contributes toward photochemical smog

How do CFCs break down the ozone layer?

free radical substituition

What is the overall equation for the decomposition of ozone?

2O₃ → 3O₂

What is the initiation step for the breakdown of ozone?

Cl₂ → 2Cl∙

What are the propagation steps for the breakdown of ozone?

1. Cl∙ + O₃ → ClO∙ + O₂
2. ClO∙ + O₃ → 2O₂ + Cl∙