Chapter 14 Alcohols Flashcards
what is an alcohol
an organic compound with the OH (hydroxyl) functional group
what are the two ways to name an alcohol
-ol suffix
hydroxy- prefix
what is the general formula for an alcohol
CnH2n+1OH
what does polyhydric mean
multiple alcohol functional groups attached
what is the shape and bond angle of the OH functional group when bonded to a carbon
bent
104.5
what is vital when drawing the skeletal formula of an alcohol
the bond from the carbon must be drawn to the oxygen not the hydrogen
why are alcohols normally water soluble
> O-H is polar due to big difference in electronegativity
>this allows the H in the OH to hydrogen bond to the O in H2O
why do long chain alcohols not normally dissolve in water
since the carbon chain is so long a large part of the organic compound is hydrophobic
what can help increase the solubility of an alcohol
adding more OH groups along the chain
what two physical properties other than solubility do the hydrogen bonds allow the alcohol to have
high melting point
high boiling point
what two reactions can take place to form alcohols
hydration of alkenes
fermentation of alkenes
what are the three conditions required for the hydration of alkenes to form alcohols
> 100C temp
high pressure
acidic catalyst (phosphoric acid)
why do alcohols produce a blue flame when combusted
the OH group means that the compound is already partially oxidised so burns well
what does [O] represent
an oxidising agent
what are the products of an oxidation of alcohol reaction dependent on
whether the alcohol is primary, secondary, tertiary
what happens when a primary alcohol is oxidised
initially an aldehyde is produced as long as the solution is distilled immediately along with water. if continuously heated (refluxed) a carboxylic acid is produced
what can you use to determine what type of organic compound the solution is
find the boiling point which acts as a diagnostic
aldehyde has the lowest and carboxylic acids the highest
what is a reflux reaction
when you heat something more strongly with an excess of an oxidising agent
what happens when a secondary alcohol is oxidised
the alcohol is refluxed to produce a ketone and water
what happens when you try to oxidise a tertiary alcohol
tertiary alcohols can’t be oxidised so no reaction takes place
what is the oxidising agent that is normally used
acidified dichromate(VI) (Cr2O7)^2-/H+
what observation can be made when an oxidation of an alcohol reaction takes place
the acidified dichromate makes the solution orange to begin then turns green when the chromium is reduced to Cr3+
why do aldehydes have the lowest boiling point
it only has induced dipole-dipole intermolecular bonds
why do alcohols have the middle boiling point
their OH allows for hydrogen bonding intermolecular forces
why do carboxylic acids have the highest boiling point
they have both induced dipole-dipole and hydrogen bond intermolecular forces
what are the 5 reactions that alcohos can undergo
combustion oxidation dehydration esterification substitution
what happens during a dehydration of an alcohol
elimination reaction where the Oh functional group and one hydrogen from one of the adjacent carbon are removed to form an alkene and water
what are the two conditions required for a dehydration reaction
reflux
acid catalyst
what happens during an esterification reaction
alcohol is reacted with a carboxylic acid to produce an ester and water
how is the water molecule produced during esterification
the OH from the carboxylic acid and the H from the OH in the alcohol bond to form the water to allow the rest of the compound to bond
what is the functional group of an ester
C-O-C=O
what is a substitution reaction
reaction where one functional group is replaced by another
give an example of one substitution reaction alcohols can undergo
alcohol + hydrogenhalide –> haloalkane + water
what are the two possible conditions for a substitution reaction with a hydrogenhalide
reflux with hydrogenhalide
or
use sodiumhalide plus concentrated sulfuric acid
why is sodiumhalide used more than refluxing for the substitution to form a haloalkane
the hydrogenhalide is produced in situ meaning that it is safer and uses less energy
