Comparing the rates of hydrolysis reactions Flashcards
when wanting to observe a hydrolysis reaction, we use……….instead of water because……..
silver nitrate solution instead of water because the reaction using just water takes more time
silver nitrate can be used in a test for
halide ions
silver nitrate can be used to test for halide ions because
the silver ions in the silver nitrate react with the hlide ions formed in the hydrolysis to give a precpitate
the equation for the reaction between silver ions and the halide ions is
Ag+ + X- = AgX
the practical involving the reaction of silver nitrate and a halogenoalkane uses
ethanol as a solvent for the mixture
an alcohol is used for the reaction mixture between silver nitrate and a halogenoalkane because
halogenoalkanes and aqueous silver nitrate do not mix, and form separate layers
we can compare the rates of hydrolysis between different halogenoalkanes by using
silver nitrate dissolved in ethanol
the reaction between silver nitrate and a chloroalkane dissolved in ethanol will produce
no precipitate
the reaction between silver nitrate and a bromoalkane dissolved in ethanol will produce
a faint cream-coloured precipitate
the reaction between silver nitrate and a iodoalkane dissolved in ethanol will produce
a pale yellow precipitate
we can compare the rates of of hydrolysis reaction using;
a comparison of halogenoalkanes with the same structure but different halogens
or
a comparison of halogenoalkanes with the same halogen but different structure
using our knowledge of electronegativity and the consequent polarity of the bond, we would expect
fluorine to have the fastest hydrolysis, followed by oxygen and so on in the order of Group 7
why is it that fluoroalkanes are so unreactive in hydrolysis that they are omitted from comparison experiments with other halogenoalkanes?
fluorine is the most electronegative element in the Periodic Table, meaning it form very polar bonds with carbon in fluoroalkanes. This means a lot of energy is required to break the bond, so a reaction with the OH group in the water is less likely to happen as more energy is required to break this bond than it would be to break an iodine-carbon bond in an iodoalkane
the trend for the rate of reactivity in hydrolysis reaction for halogenoalkanes with halogen atoms going down Group 7 is
the reaction gets faster from Cl to I as iodine has the lower electronegativity, so forms less polar bonds which are easier to break as they require less energy to break than the more polar chlorine-carbon bonds
when comparing the rates of hydrolysis reaction with halogenoalkanes of different structure but the same halogen atom, the trend is
that primary halogenoalkanes react more slowly than tertiary or secondary halogenoalkanes
