4D- Alcohols

important thing to remember when drawing structure of alcohol to do with bonds

bond from the carbon connects to the oxygen atom no the hydrogen atom

what is the prefix used for alcohol when there is a higher priority group

hydroxy

how do you name a molecule with more than one OH group

suffix -diol and ‘e’ is added to the parent chain name e.g. butane-2,3-diol

how can you classify alcohols

primary, secondary and tertiary

what is a primary alcohol

-OH group is attached to a carbon attached to two hydrogen atoms

what is a secondary alcohol

-OH group is attached to a carbon that is attached to one hydrogen atom

what is a tertiary alcohol

-OH group is attached to a carbon that is attached to no hydrogen atoms

how do you compare alcohols to alkanes (relating to chain length)

include the oxygen atom as a carbon e.g. compare ethane with methanol not ethanol

what is the difference between melting and boiling points of alcohols with alkanes and why

alcohol have higher melting and boiling points, polar molecules so have hydrogen bonds which are stronger than London Forces

how does solubility in alcohol compare to alkanes and why

alcohols soluble, -OH group can hydrogen bond with water, hydroxyl group is hydrophilic

why is it appropriate to compare alkanes with alcohols that have one less carbon

so they have similar molecular masses and numbers of electrons so London Forces will be comparable and of similar strengths

how does solubility change with length of chain in alcohols and why

water solubility decreases as chain length increases, proportion of the molecule that is polar (only the -OH part that interacts with water) and can hydrogen bond with the water decreases, the effect of the -OH decreases

what is a solvent that the large alcohols will dissolve in

any non-polar solvent e.g. hexane

what are the possible reaction of alcohols

• combustion

• elimination

• oxidation

• substitution

what is a (complete) combustion reaction

reaction of a substance in a plentiful supply of oxygen to form carbon dioxide and water

what is an elimination reaction

removal of a molecule from a saturated molecule to form an unsaturated molecule

what is an oxidation reaction

increase in oxidation number/loss of electrons

what is a substitution reaction

reaction where an atom or group of atoms is replaced by a different atom or group of atoms

what can elimination reactions also be known as in alcohols

dehydration reaction

what conditions are needed in an elimination reaction of an alcohol

• concentrated acid catalyst in excess (e.g. H₂SO₄ or H₃PO₄)

• heated under reflux

what happens in an elimination reaction of an alcohol

the -OH group is lost together with a H atom from the next carbon atom to form water

which alcohols can produce multiple products in an elimination reaction

secondary and tertiary

what are three advantages of using ethanol as a fuel

• quite soluble in water

• releases lots of energy in complete combustion

• helps reduce emissions of air toxins

how can you recognise an elimination reaction

water is formed, 1 molecule to 2 molecules, increase in the number of double bonds

what are the conditions required to produce an ether

an excess of alcohol, two alcohol molecules are then more likely to join together to form an ether

what does a substitution reaction with alcohols produce

a haloalkane

what reactants and conditions are needed for a substitution reaction of an alcohol

sodium halide e.g. NaBr and sulfuric acid, heated under reflux

what happens in a substitution reaction of an alcohol

the sodium halide and sulfuric acid react together to produce a hydrogen halide in situ, this hydrogen halide then reacts with the alcohol to form a haloalkane

what are the equations for the steps in a substitution reaction of an alcohol

Step 1: NaX + H₂SO₄ → HX + NaHSO₄
Step 2: HX + alcohol → H₂O + haloalkane

overall reaction: alcohol + NaX + H₂SO₄ → haloalkane + NaHSO₄ H₂O

what is the oxidising agent for alcohols in an oxidation reaction

acidified potassium dichromate solution- K₂Cr₂O₇ mixed with H₂SO₄

what observations can be made if a successful oxidation reaction occurs

reaction mixture turns from orange to green (or blue)

what are the types of oxidation for a primary alcohol

mild oxidation and stronger oxidation

how do you show oxygen as a reactant in oxidation reactions of alcohols

[O]

what does a mild oxidation of a primary alcohol form

an aldehyde

what is the equation of a mild oxidation of a primary alcohol- ethanol

CH₃CH₂OH + [O] → CH₃CHO + H₂O

what is the functional group of an aldehyde

C=OH

what is the suffix for an aldehyde

-al e.g. ethanal

what does a strong oxidation of a primary alcohol form

a carboxylic acid

what is the equation of the 2nd oxidation of a primary alcohol (from an aldehyde)- ethanol initially

CH₃CHO + [O] → CH₃COOH

what is the overall equation for the full oxidation of a primary alcohol- ethanol

CH₃CH₂OH + 2[O] → CH₃COOH + H₂O

what is the functional group of a carboxylic acid

-COOH

what is the suffix of a carboxylic acid

-oic acid e.g. ethanoic acid

how do you control the oxidation of primary alcohols to only form an aldehyde

remove aldehyde from reaction mixture as soon as it forms by distillation

what is the equipment set up needed to make and aldehyde from a primary alcohol

distillation

what conditions are needed to make a carboxylic acid from a primary alcohol

heat under reflux with excess acidified potassium dichromate solution

what is the set up of the equipment to make a carboxylic acid from a primary alcohol

heat under reflux

what does the oxidation of secondary alcohols form

a ketone

what is the ketone functional group

C=O

what is the suffix for a ketone

-one e.g. propanone

what is the equation for making a ketone from a secondary alcohol- propan-2-ol

CH₃CH(OH)CH₃ + [O] → CH₃COCH₃ + H₂O

what are the conditions needed for making a ketone from a secondary alcohol

heat under reflux with excess acidified potassium dichromate solution

what does the oxidation of a tertiary alcohol form

no reaction, do not oxidise- no C-H bonds to break in order to increase the number of bonds to oxygen

define reflux

the continual evaporating and condensing of a reaction mixture to prevent the loss of volatile components

define nucleophilic substitution

a nucleophile is an atom or group of atoms which is attracted to an electron deficient carbon atom where it can donate an electron pair forming a new covalent bond

substitution reaction is where one atom or group of atoms is replaced by a different atom or group of atoms

what are ester made from

a carboxylic acid and an alcohol

what do a carboxylic acid and an alcohol form

an ester and water

what are the conditions needed to make an ester

concentrated H₂SO₄ catalyst and heating under reflux

what type of reaction is making an ester

a condensation reaction that is also reversible

what are esters commonly used as

perfumes and flavourings as they often smell sweet and fruity

how do you name an ester

• side attached to the single bonded O (from the alcohol) is named first

• gets suffix -yl

• carbon attached to the O is C1 when numbering on this side

• side of ester group attached to C=O (from acid) is named second

• gets suffix -oate

• the C in the C=O counts as part of the chain and is always C1 when numbering on this side

esters can look different in structural formula depending which way around they are drawn

how do you find the alcohol and carboxylic acid used to make an ester

break the bond between the carbon and oxygen