Unit 3) SYNTHESIS -alcohols and ethers Flashcards
what are alcohols
- alcohol are substituted alkanes in which one or more of the hydrogen atoms is replaced with a hydroxyl functional group(-OH)
why do alcohols have significantly higher boiling points than many other organic compounds with similar numbers of electrons per molecule with similar shapes?
- due to presence of polar -OH group. this allows hydrogen bonds to be set up between the molecules. as hydrogen bonds are stronger than ldf and pdp pdp interactions, extra energy is required to break them
as chain length of alcohols increases , the solubility _____. Why?
decreases.
- alcohols with small chain length are miscible with water as they can hydrogen bond with water molecules, longer chain alcohols are insoluble in water. so solubility decreases as the long non polar hydrocarbon part of alcohols masks the polar -OH group.
the viscosity of alcohols increases as the size of the molecules ____. Why?
increases
- the strength of the intermolecular forces increases as the size of the molecule increases , so more intermolecular forces are holding the molecules more firmly in place
how can alcohols be prepared / formed
- monohaloalkanes, by heating them under reflux with aqueous sodium/potassium hydroxide - this is nucleophilic substituation
- alkenes by reaction with water using sulfuric acid as catalyst - this is acid catalysed addition or hydration with alkenes
- aldehydes and ketones can be reduced reacting with a reducing agent lithium aluminium hydride (LiAlH4) dissolved in ethoxyethane
look at drawings in notes
ketone is reduced to form a ____ alcohol
aldehyde is reduced to form a ____ alcohol
secondary
primary
what can alcohols react with
- reactive metals to form alkoxides
- aluminium oxide/ conc sulfuric acid /conc phosphoric acid to form alkenes
- carboxylic acids to form esters
- oxidising agents to form aldehydes / ketones
alcohols reaction with reactive metals eg sodium/potassium
- what does it form
- give an example
- what kind of reaction is this
- forms alkoxides
- sodium reacts with ethanol to form sodium ethoxide
- displacement/redox
alcohols reacting with aluminium oxide / conc sulfuric acid/ conc phosphoric acid
- what does it form
- example
- what type of reaction is this
- forms alkenes
- propan 1 ol reacting with aluminium oxide to form propene
- this is an elimination or dehydration reaction
alcohols reacting with carboxylic acids/ acid chlorides
- what does it form
- example
- what type of reaction is this
- forms esters
- ethanoic acid ( carboxylic acid) reacting with ethanol (alcohol) forms ethyl ethanoate (ester)
- condensation reaction / esterification
alcohols reacting with oxidising agents eg copper ii oxide or acidified potassium permanganate
- what does it form
- example
- what is this reaction called
- forms aldehydes / ketones. primary alcohols oxidise to aldehydes and secondary alcohols are oxidised to ketones
- ?
- oxidation
what is an ether
ethers can be regarded as substituted alkanes in which a hydrogen atom is replaced with an alkoxy functional group -OR ( the r can be several Cs with HS )
naming ethers
- look at notes i made / bright red page 61
ethers are ____ of alcohols
isomers
why do ethers have much lower boiling points than their isomeric alcohols ?
- because hydrogen bonding does not occur BETWEEN ether molecules. this is because the highly electronegative oxygen atom is not directly bonded to a hydrogen atom. ether molecules can however hydrogen bond with water
