Organic Chapter 3: Alkenes & Alcohols Flashcards
What is an alkene?
An unsaturated hydrocarbon, represented by the formula CnH2n
Always have at least 1 C=C double bond.
How can you test for alkenes?
Add bromine water; it will go colourless if an alkene is present
What reactions do alkenes undergo?
Electrophilic addition
What is the order of stability between carbocations?
Primary is least stable
Tertiary is most stable
What is a primary carbocation?
A carbocation where there is 1 R group attached to a carbon.
What is a secondary carbocation?
A carbocation where there are 2 R groups attached to a carbon
What is a tertiary carbocation?
A carbocation where there are 3 R groups attached to a carbon
Why are there multiple possible products when you add hydrogen halides to unsymmetrical alkenes?
Different carbocation intermediates can form
What are polymers made from?
A long string of monomers
How do the IMFs of polymers affect their properties?
Long, straight chaned polymers tend to be strong & rigid
Short & branched chains tend to be weaker & more flexible
Why would you plasticise a polymer?
To make it more flexible
How can you find the repeating unit monomer from a polymer?
Remove the C=C double bond & draw the groups vertically around it (repeating unit should only be 2 carbons long)
What is an Alcohol?
A chemical that has the hydroxyl group, -OH.
Represented by the formula CnH2n+1OH
What is a Primary alcohol?
An alcohol where there is 1 R group on the Carbon attached to the OH.
Secondary = 2 R groups
Tertiary = 3 R groups
What do alcohols form when dehydrated?
Alkenes
What are the three stages of distillation?
Distilation
Separation
Purification
What happens in the distillation stage of distillation?
The mixture will be acidified & heated gently with anti-bumping granules in it.
The chemicals with lower boiling points will evaporate, rise up, and then be collected in a flask, from the condenser.
What happens in the separation stage of distillation?
The product from distillation will be poured into a separating funnel & mixed with water. This will dissolve all the water-soluble impurities & create an aqueous solution, which will then form as a layer.
Drain the aqeous lower layer, leaving the impure product.
What happens in the purification stage of distillation?
Drain the impure product from separation into a round-bottomed flask.
Add a drying agent (such as anhydrous CaCl2) and let the mixture dry for aorund 20 minutes.
Distill the mixture formed one last time to get a pure product.
How are alcohols produced?
Hydration of alkenes
Fermentation
How does fermentation of alcohols work?
C6H12O6 -> 2(C2H5OH) + 2(CO2)
Reaction is carried out by yeast under anaerobic conditions
Enzyme produced by yeast works the best at 30-40 degrees
Cheap equipment & renewable resources used
What are some advantages of biofuels?
- Renewable
- Carbon neutral due to plants
What are some disadvantages of biofuels?
- Car engines & other tech needs to be changed to use them
- Land used to grow fuel crops can’t be used for food
- Not entirely carbon neutral; need to be transported
How does hydration of alkenes compare to fermentation?
300 degrees celcius & 60atm pressure - high cost
Faster
What are primary alcohols oxidised to form?
Aldehydes & then carboxylic acids on further oxidation
What are secondary alcohols oxidised to form?
Ketones
What are Tertiary alcohols oxidised to form?
They cannot undergo further oxidation
How can you tell aldehydes & ketones apart?
Tollen’s reagent will form a silver mirror when warmed with a ketone
