Alcohols Flashcards
How are alcohols named?
by replacing the -e of the alkane with -ol.
also numbered to give the carbon with the attached OH group the lowest number. e.g 2-butanol
What are the main physical properties of alcohols?
weak acids (weaker than water) higher boiling points and greater solubility than alkenes, alkanes, aldehydes, ketones and alkyl halides oxygen in alcohol can act as a proton donor or acceptor
What is the general trend for acidity of alcohols?
Acidity decreases with increasing number of attached carbons.
Primary alcohols are more acidic than secondary alcohols which are more acidic than tertiary alcohols.
What is the general trend for reactivity of alcohols?
Tertiary alcohols are more reactive than secondary alcohols which are more reactive than primary alcohols.
What happens with alcohols as the carbon chain increases?
The non-polar chain becomes more meaningful and the alcohol less water soluble.
What is dehydration?
What is produced and what are the requirements?
Dehydration is the loss of water.
Leads to the production of alkenes.
Requires a high temp (300°C) and a metal oxide catalyst (Al2O3) OR reflux with a hot acid (H2SO4 (conc)).
What is oxidation/reduction?
Oxidation increase in oxygen or decrease in hydrogen content.
Reduction is the opposite.
What are the products of oxidation of primary alcohols?
primary alcohol => aldehyde (mild oxidising agents (CrO3) or powerful oxidising agents (K2CrO7/H2SO4) under mild conditions)
primary alcohol => carboxylic acid (KMnO4 under abrasive conditions)
What are the products of oxidation of secondary alcohols?
secondary alcohol => ketones (any of the above oxidising agents for primary alcohols)
What is substitution in alcohols?
Substitution occurs when the OH group is replaced by a halide (Cl or Br)
What type of reaction is the Sn1 mechanism of alcohol substitution?
First order nucleophilic substitution
What does the rate of reaction depend on for the Sn1 mechanism?
The rate of the reaction depends on the concentration of R(alkyl)-L(ligand)
The RDS is the formation of the carbocation
What are the steps in the Sn1 mechanism of alcohol substitution?
R-L => R+ + L-
Nu- + R+ => Nu-R
R+ is a carbocation (transition state)
What type of reaction is the Sn2 mechanism in alcohols?
Second order nucleophilic substitution.
What does the reaction rate depend on in the Sn2 mechanism of alcohol substitution?
the conc of two compounds:
first order with respect to [Nu-]
first order with respect to [R-L] )
