organic synthesis Flashcards
how do you form a Grignard reagent
halogenoalkane dissolved in dry ether and reacted with magnesium
what can the aklyl group be considered to have
a negative charge, therefore it can behave as a nucleophile
R-[+MgI]
what can grignard reagents react with methanal to produce
a primary alcohol
RMgI + HCHO -> RCH2OH + Mg(OH)I
when you react Grignard reagent with longer chain aldehyde what can you produce
secondary alcohols
CH3CH2MgI + CH3CHO –> CH3CH2CH(OH)CH3 + Mg(OH)I
what do ketones react with Grignard reagents to produce
tertiary alcohol
CH3CH2MgI + CH3COCH3 –> CH3CH2C(CH3)(OH)CH3 + Mg(OH)I
what does grignard and carbon dixoide produce
a carboxylic acid
CH3CH2MgI + CO2 –> CH3CH2COOH + Mg(OH)I
when is steam distillation used
to separate an insoluble liquid from an aqueous solution
Steam is bubbled through a reaction mixture containing the aqueous solution and the insoluble liquid that forms a separate layer
As the steam bubbles through the reaction mixture it mixes the layers so they form part of the evaporating liquid
advantages of steam distillation
The insoluble liquid distills at a temperature below its usual boiling point
It reduces the chances of thermal decomposition of the insoluble liquid
how does recrystallisation work
used to purify impure solids
The principle is that a hot solvent is used to dissolve both the organic solid and the impurities and then as the solution cools the solid crystallises out and leaves behind the impurities in the solution
what do impurities do to the melting point
Impurities tend to lower the melting point of a solid
Pure substances have sharp well defined melting points
Impure substances have a broad melting point range, a large difference between when the substance first melts until it completely melts
what do impurities do to boiling temperature
The boiling point may appear higher than the literature / database values
The sample may boil over a range of temperatures instead of at a single temperature
