alcohols Flashcards
what are the two ways to make an ethanol (alcohol)
fermentation and hydration of ethene
what are the conditions for fermentation
room temperature, yeast and no oxygen (anaerobic respiration)
what are the conditions needed for the hydration of ethene
fractional distillation at 300°C, 70 atm and a catalyst ( conc° H₃PO₄- phosphoric acid)
what are the pros of fermentation
low energy needed, sugar is renewable, lower tech demands
what are the cons of fermentation
its a slow batch process, less efficient, the ethanol made is impure and it depletes land used to grow crops
what is the equation for fermentation
glucose → ethanol + carbon dioxide
C6H12O6 →2 CH3CH2OH + 2 CO2
why is fermentation done without air
it will oxidise the ethanol produced to ethanoic acid (vinegar)
what are the pros of hydration of ethene
its a fast reaction, the product is pure, its a continuous process
what are the cons of hydration of ethene
high tech needed which inc costs, ethene is non-renewable and lots of energy is needed which also make it more expensive
what is the general formula of alcohols
CnH2n+1OH
what are the boiling points of alcohol
they are relatively low, due to their ability to form hydrogen bonds between alcohol molecules
explain the trend in solubility of alcohols
the smaller the alcohol, the more soluble thy are because they can form hydrogen bonds to water.
The longer the chain the less soluble the alcohol
what are the three types of alcohols
primary, secondary and tertiary
what is the bond angle of an alcohol
H-C-H bond and C-C-O bond are 109.5° (tetrahedral, there are 4 BP), whereas the H-O-C bond is 104.5° (bent, there are 2 BP and 2LP)
what is the reaction for the combustion of alcohols
CH3CH2OH + 3O2 → 2CO2 + 3H2O, it reacts with a clean flame
what is the reaction of alcohols with sodium
2CH3CH2OH + 2Na → 2CH3CH2O-Na+ + H2, can be used as a test for alcohols
what are the observations when alcohol reacts with sodium
effervescence (bubbles), mixture gets hot (endothermic), sodium dissolves and a white solid is produced
what are the conditions of oxidation of alcohols
mild (gentle heating,)
what is formed when primary alcohols are oxidised under mild conditions
they form aldehydes (which are volatile) and need to be distilled
what is formed when primary alcohols are oxidised under stronger heating and excess oxidising agent
they form carboxylic acid
why do aldehydes need to be distilled
to prevent further oxidation to form carboxylic acid
how is an oxidising agent represented in a reaction
[O]
what are the reagents for the partial oxidation of an alcohol
potassium dichromate (K2Cr2O7) an dilute sulfuric acid (H2SO4)
what are the conditions for partial oxidation of primary alcohols
use a limited amount of dichromate and mild temp to gently distil out the aldehyde as it forms
what is an observation of the partial oxidation of a primary alcohol
the orang dichromate ion (Cr2O7^2-) reduces to the green Cr^3+ ion
what
thermometer, 2 round bottom flasks, a liebig condencer, water, ice and an electric heater
why is an electric heater used to heat alcohol
as alcohols are very flammable using an open flame is very dangerous
what is the full oxidation of primary alcohols
using an excess of potassium dichromate (VI) (K2Cr2O7) and dilute sulfuric acid (H2SO4), heat under reflux , this produces carboxylic acid which will need to be distilled at the end
