WM Flashcards
physical properties of alcohols
polar due to polarised OH bond
hydrogen bonding present so higher BPs than corresponding alkanes
ability to mix with water due to hydrogen bonds
effect of alcohol chain length on influence of OH group
as chain becomes longer, influence of OH group becomes less important
the larger the alcohol the more similar it is to its corresponding alkane
therefore solubility decreases as length increases
primary alcohols
OH group attached to carbon which is bonded to only one other carbon
can be oxidised
secondary alcohols
OH group attached to a carbon which is bonded to two other carbons
can be oxidised
tertiary alcohols
OH group attached to a carbon which is bonded to three other carbons
cannot be oxidised due to no hydrogen atom on the carbon atom to which the OH group is attached
oxidation of primary alcohols
aldehyde (no reflux and alcohol in excess)
aldehyde then carboxylic acid (reflux and oxidising agent in excess)
oxidation of secondary alcohols
ketone and water formed (reflux with oxidising agent in excess)
refluxing
safe method of heating flammable, volatile liquids
dichromate ion as an oxidising agent
dichromate ion (orange)»_space; chromate (III) ion (green)
dehydration of alcohols
alcohols can lose a molecule of water to form an ALKENE
conditions: heated alumina (Al2O3) catalyst, or reflux with c. H2SO4
nucleophilic substituion of alcohols
alcohols undergo nucelophilic substitution with halides in the presence of strong acid to produce haloalkanes
esterification using alcohol and carboxylic acid
produces ester and water
very slow reaction unless a strong acid catalyst is used and is heated under reflux
acid anhydride + alcohol»_space;
ester + carboxylic acid
requires warming but produces high yield of ester
phenol + acid anhydride»_space;
ester + carboxylic acid
requires alkaline conditions
OH group in phenol is much less reactive so requires a more vigorous reagent to esterify it - acid anhydride
purification of organic liquid products
during synthesis of organic liquids a crude product is usually produced
purified using separating funnel, drying agents or simple distillation
test for phenol (and its derivatives)
go purple on addition of iron (III) chloride
producing aspirin (2-ethanoyloxybenzoic acid) from salicylic acid
phenol group of salicylic acid reacts with acid anhydride
forms ester group
producing oil of wintergreen (methyl 2-hydroxybenzoate) from salicylic acid
-COOH group on salicylic acid reacts with methanol (forms ester group)
infrared spectroscopy
substances exposed to IR
molecules absorb IR of different frequencies
causes vibrational energy changes to occur within molecules
bond deformation in infrared spectroscopy
diatomic molecules can only vibrate by stretching so they have just one vibrational infrared absorption
in more complex molecules, more bond deformations are possible (most involve more than two atoms)
fingerprint region
region on infrared spectroscopy below 1500cm^-1
useful to compare spectra to find out if they are of the same compound
rarely used to identify functional groups
mass spectrometry
used to find the atomic mass of elements and the relative abundances of isotopes in elements
can be used to identify more complex molecules
molecular ion M+
heaviest ion in the mass spectra
corresponds to the original compound with one electron removed
green chemistry
developing chemical products and processes that are as sustainable and environmentally friendly as possible
key factors to consider for chemical processes:
cost, impact on environment, health and safety
changing reagents to improve atom economy may increase cost
changing reagents may raise new health and safety issues
reducing overall number of steps in process may reduce yield
lowered temperature may increase reaction time and hence cost
