colour by design Flashcards
bonds attaching dyes to fibres
- hydrogen bonds
- ionic bonds
- covalent bonds
- id-id bonds
- pd-pd bonds
hydrogen bonds and attaching dyes to fibres
- hydrogen bonds are formed between OH groups on fibre molecules and some dyes (like those with an NH2 group)
ionic bonds and attaching dyes to fibres
- ionic bonds may bind a dye to a fibre
- this is usually with an -NH3+ group on the fibre and -SO3- on the dye
covalent bonds and attaching dyes to fibres
covalent bonds are strongest and dyes which bond covalently have a functional group which will react with the fibre
id-id bonds and attaching dyes to fibres
id-id bond can also bind a dye to a fibre, usually only happens with small dye molecules since the bonds are very weak
pd-pd bonds and attaching dyes to fibres
pd-pd bonds can occur alongside hydrogen bonding when both the dye and fabric are polar (pd-pd is stronger than id-id)
functional groups of fibres
most fibres have functional groups which dyes bind to, such as
COOH
NH
CONH
what are fibre reactive dyes
Dyes which form covalent bonds with the fabric
what are colour fast dyes
dyes that don’t fade or wash out very easily due to strong bonds between the dye and fabric - (typically only ionic bonds and covalent bonds are strong enough to be colourfast)
chromophore definition
the part of a dye which gives it its colour (a chain of double and single bonds)
functional groups that affect dye solubility
ionic groups such as sulfonate (SO3 2-)
structure of fats and oils
mixed esters of propane-1,2,3-triol with varying degrees of saturation
triglyceride structure
one glycerol (propane-1,2,3-triol) constant and three fatty acid chains long chained carboxylic acids that vary
triglyceride formation
condensation reaction between glycerol and three fatty acids
triglyceride breaking
hydrolysis reaction, alkane solution (NaOH) and head under reflux conditions required
features of saturated fatty acids
contain only C-C single bonds
form straight chained molecules
pack closely together
high density
have higher bpt/mpt due to stronger intermolecular forces (id-id), heavier fats e.g. lard
features of unsaturated fatty acids
contain C=C double bonds
monounsaturated (one C=C) or polyunsaturated (many C=C bonds)
form kinks in structure
can’t pack as close together
lower density
weaker imf (id-id), so lower bpt/mpt
difference between fats and oils
oils have mpt below room temp
fats have mpt above room temp
features of arenes
- cyclic hydrocarbons
- planar shape
- the pi electrons are stabilised by electron delocalisation
- the number of pi electrons is 4n+2
phenyl group meaning
a benzene ring with one H replaced by another group
what is an aromatic compound
a molecule with a benzene ring
naming arenes
all groups attached to a benzene ring use the suffix ‘-benzene’
if benzene is not the main functional group, benzene is shown through the prefix ‘phenyl-‘
benzene and addition reactions
benzene does not easily take part in addition reactions because
- delocalised electrons stabilise benzene
-any disruption of electrons makes benzene unstable
benzene and substitution reactions
benzene will readily undergo substitution reactions with electrophiles
this is because the ring system is electron rich and will attack positive centres
electrophile definition
accepts a pair of electrons to make a covalent bond
position of delocalised ring in benzene
delocalised ring is above and below the plane of the molecule, made from p-orbitals
Hydrogenation evidence for the delocalised model of benzene
- Hydrogenation is a reaction where H2 is added to an alkene to remove its double bonds
- Cyclohexene is a six-carbon ring with one double bond
- Its hydrogenation enthalpy change is −120kJmol-1
- With the three double-bond structure of benzene, it would have a hydrogenation enthalpy change of 3× this
- However, experimental evidence suggests that it’s much less exothermic than this
- This is explained by the delocalised ring’s increased stability - more energy would be needed to hydrogenate it
polyfunctional molecules meaning
molecules that have multuple functional groups