alcohols chp 14 Flashcards
what gives alcohols there physcial and chemical properties
The Hydroxyl group (-OH)
what are some difference between the characteristic of alcohols and alkanes
- they have higher melting/boiling points
- they have greater water solubility (than there corresponding alkanes)
- The differences become smaller as chain length increases
Descibe and explain what effect the polarity of alkanes has on its characteristics
- non-polar due to electronegativity similarity bonding elements
- intermolecular forces between non-polar molecules are very weak London forces leads, to low melting and boiling points
- insoluble in polar solvents
- soluble in non-polar solvents
Descibe and explain what effect the polarity of alcohols has on its characteristics
- alcohols are polar due to presence of OH group making them soluble in some polar solvents
- higher melting and boiling points than respective alkanes
what does the trend in boiling points between alcohols and alkanes look like
define Volatility
how easily a substance will vaporize
volatile liquids have a low boiling point
what alcohols if any are soulble in water and explain why they are
alcohols such as methanol and ethanol are completely soluble in water as hydrogen bonds form between the polar OH groups of the alcohols and the water molecules
Longer chain are less soluble due to the effect of the OH group becomeing less prevelant with increasing chain length
what is a primary alcohol
- OH group in alcohol attached to carbon attached to 2 hydrogens and a single carbon
- 3 hydrogens in methanol case
what is a secondary alcohol
The alcohol is OH group is attached to a carbon atom that is attached to 1 hydrogen atom and 2 alkyl groups
what is a tertiary alcohol
The OH group is attached to a carbon atom that is attached to no hydrogen atoms and 3 alkyl groups
can alcohols be oxidised, if so which alcohols
- Primary and secondary alcohols can be oxidised (using [o], acidfied potassium dichromate(VI) K2Cr2O7/H+)
- Tertiary alcohols cannot be oxidised
what colour change occurs when alcohols are oxidised
orange to green
what are primary alcohols oxidised into
-Primary alcohols can be oxidised to either aldehydes or carboxylic acid
-The product of the oxidation depends on the reaction conditions used (aldehydes are themselves oxidised to carboxylic acids)
how do you obtain aldehydes from alcohols
- distill primary alcohols with acidified potassium dichromate
- how do you obtain a carboxylic acid from an alcohol
- write reaction
- reflux primary alcohol with excess acidified potassium dichromate (VI) (ensures all alcohol is oxidised)
- reflux ensures any aldehyde formed undergoes oxidation to form carboxylic acid.
what are secondary alcohols oxidised into
They are oxidised into ketones (it is not possible to further oxidise ketones using acidified dichromate ions)
what is the process to obtain a ketone from a secondary alcohol
you heat the secondary alcohol under reflux with excess acidified dichromate ions
-you heat under reflux to ensure that all alcohol has been reacted - you add excess to ensure that the all the alcohol is allowed to react -There will be a colour change from orange to green
what is a dehydration reaction
dehydration is any reaction in which a water molecule is removed from the starting material
whats the process to dehydrate an alcohol
- heat alcohol under reflux in presence of acid catalyst conc H2SO4, or conc (phosphoric acid) H3PO4.
- produces alkene
what are the products of a dehydration reaction with an alcohol
water + alkene
what type of reaction is a dehydration reaction
An elimination reaction
what is a substitution reaction
an atom, ion, or group of atoms or ions in a molecule is replaced by another atom, ion, or group
What is an example of a substitution reaction that alcohols can undergo
alcohols react with hydrogen halides to form haloalkanes
what is the process to produce a haloalkane from an alcohol
- alcohol is heated under reflux with sulphuric acid and a sodium halide,
- ^hydrogen halide is formed which reacts with alcohol to produce a haloalkane, salt and water
what does the hydrogen halide reaction with the alcohol chemical equation look like
