(yellow) Alcohols Flashcards
(yellow) Alcohols
waht are alcohols at room tempreture
liquid
Why are alcohols less volatile than the corresponding alkane?
OH, hydroxyl group can make H-bonds between adjacent molecules.
These are stronger than the London forces between alkanes
So more heat energy is required to overcome them, leading to higher B Pts.
Explain why hydrogen bonding accounts for the fact that methanol, at room temperature, is a liquid that mixes freely with water, while ethane is a gas which is insoluble in water.
Both have similar number of electrons and London forces
Methanol can form H-bonds with water so mixing with it.
Ethane can only form weaker London forces so cannot disrupt the H-bonds between the water molecules.
what is the definition of a elimination reaction
Elimination reaction is the removal of one or more groups or atoms from adjacent C atoms forming an unsaturated molecule.
what is the definition of a dehydration reaction
Dehydration is the removal of a water molecule – water is the only inorganic product formed in the reaction
how do you go from an alcohol to a alkene
conc phosphoric acid / H2SO4 (catalyst)
this forms an alkene + water
what is the definition of nucleophile
Nucleophile
An electron rich species with an available lone pair of electrons
May be negatively charged
Reacts by donating a pair of electrons to form a new covalent bond to a carbon atom.
what is the definition of a substitution reaction
Substitution reaction
Where one group replaces another in a molecule e.g. when an alcohol forms a chloroalkane . OH group is replaced by Cl atom
how do you go from an alcohol to a chloro alkane
give reagents and conditions
PCl5
R-OH + PCl5 —-> R-Cl + POCl3 + HCl
or HCl
how do you go from alcohol to bromoalkane
give reagengts and conditions
heat under reflux
conc H2SO4
conc KBr
which produces HBr in situ
KBr + H2SO4 —> HBr + KHSO4
HBr + CH3CH3CH2OH —> CH3CH3CH2Br + H2O
propanol as an example
how do you go from an alcohol to an iodine alkane
give reagents and conditions
moist red phosphorus and iodine this produces PI3 in situ
3 CH3OH + PI3 —-> 3 CH3I + H3PO3
heat under reflux
what is the colour change when you reduce chromium from +6 to +3
orange to green
how do you know if a reaction has taken place in a oxidation potassium dichromate reaction
the colour of the solution has turned from orange to green
how do you oxidise alcohols
give reagents and conditions
reagents K2Cr2O7
H2SO4
reflux / disstilation
orange to green
what is the pecie of aparatus called that connects the tap funnel, condensor and pear shaped flask together in distilation
still head
some water may be lest behind after drying name some drying agents
silica
CaSO4
MgSO4
Na2SO4
what is the idea filtering funnel
1) Solvent extraction
* A separating funnel is used, the reaction mixture is put into this and another solvent which is immiscible (insoluble) in the reaction mixture, so two layers are seen. * The desired product must also be more soluble in the new solvent added * The idea is that the product will move into the new solvent and any impurities will remain behind in the original reaction mixture. * Then the two layers are ‘tapped off’ and the desired layer kept.
alcohols soluable in water while other organics are not
