Alcohols
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What 3 structures are found in alcohols
Primary, secondary and tertiary
What is the functional group for alcohols
OH
Draw the structures for primary, secondary and tertiary alcohols
Check physical flashcards for answers
How can alkenes be formed from alcohols?
By dehydrating alcohols
Describe a dehydration reaction and give the formula
• Eliminating water from alcohols • CnH2n+1OH -> CnH2n + H2O
How are alkenes produced from renewable resources
• Plants contain glucose and the fermentation of glucose produces ethanol
Give one industrial use for alkenes
Starting material for polymers
What is the catalyst for the dehydration of alcohols
Concentrated sulfuric acid or phosphoric acid
What is the product of the dehydration using catalysts
A mixture with water, acid and reactant so the alkene has to be separated out
Draw the mechanism for the elimination of water from ethanol
Check physical flashcards for answers
Describe the mechanism of the elimination of water from ethanol
• A lone pair of electron on oxygen bonds to an H+ from the acid. The alcohol is protonated giving the oxygen a positive charge • The positively charge oxygen pulls electrons away from carbon. The H2O leaves, leaving an unstable carbocation intermediate • The carbocation loses an H+ and an alkene is formed
Why do more complicated alcohols form more than one product?
Because the double bond can form on either side of the carbon with the OH group attached
What process is used to separate chemicals?
Distillation
Why are organic compounds purified?
They contain impurities
How is a pure alkene produced
By separating from other substances e.g products, reactant, acid and water
Why does the distillation technique work?
Different chemicals have different boiling points to separate them
Name the stages that are needed in producing cyclohexene from cyclohexanol
Distillation, Separation and purification
Describe the distillation process
• Add H2SO4 and H3PO4 to a round bottom flask containing cyclohexanol. Swirl the flask and add 2-3 carborundum boiling chips • Mixture should be gently heated to 83 degrees Celsius using a water bath or electric heater • At this temperature the chemicals will evaporate. The warm gas will rise into the condenser with cold water running through the outside which turns it into a liquid
Describe the separation stage
• Transfer the product to a separating funnel to dissolve water soluble impurities and create an aqueous solution • Allow the mixture to settle into layers. Drain the aqueous lower layer, leaving the impure cyclohexane
Describe the stage of purification
• Drain the cyclohexane into a round-bottomed flask • Add anhydrous CaCl2 and stopper the flask. Let the mixture dry for at least 20minutes with occasional swirling. • The cyclohexane will still have small amounts of impurities so distill the mixture one last time
What is the reagent for the elimination of water from an alcohol and what is the condition?
• Concentrated H2SO4/ Phosphoric acid • hot temperature
Why cant tertiary alcohols be oxidized
They have no hydrogen on the central atom