Organic Flashcards
(25 cards)
What are the properties of Alkanes?
Saturated Hydrocarbons,
Tetrahedral structure,
Non-Polar
Insoluble in water as they have no permanent dipole,
Why does the Boiling point of hydrocarbons increase as the chain length increases?
There are induced dipole-dipole forces between the molecules and as the chain length increase there is more surface area so there are more forces and the forces get bigger so they are stronger,
Branches alkanes have lower boiling points as the forces are further away,
What are the requirements for Thermal Cracking?
A high temperature and High pressure
What happens during Thermal Cracking?
The covalent bond splits and a high percentage of alkenes are produces (they are very useful in the chemical industry)
What are the conditions for Catalytic Cracking?
A high temperature,
Low pressure,
A Zeolite catalyst (it has a large surface area)
What is produced during catalytic cracking?
Often produces branched and cyclical alkanes which are good for fuel,
What is a free radical?
An atom/molecule with an unpaired electron, they are very reactive and can even react with alkanes
What happens during the initiation step of free radical substitution?
UV light in shone onto the reaction, A Halogen molecules splits into two free radicals
(e.g. Br2–> Br+Br)
What is step one of Propagation?
The Halogen free radical reacts with the alkane molecule to form an alkane free radical and one hydrogen bonded to the halogen (e.g. CH3 and HBr)
What is step two of propagation?
The alkane free radical reacts with a halogen molecule to form the desired end product and a halogen free radical which can go back and trigger step 1
(e.g. CH3+Br2–> CH3Br+Br)
What is termination?
Two free radicals collide to form a stable molecule and finish the reaction chain,
(e.g. Br+Br–> Br2,
CH3+CH3–>C2H6,
CH3+Br–>CH3Br)
What is a haloalkane?
A halogen bonded to an alkane,
What are primary, secondary and tertiary structures?
The amount of carbons that the carbon the halogen is bonded to are bonded to
Why do haloalkanes have higher boiling points than their equivalent alkanes?
There is a polar bond between the halogen and the carbon which creates a permanent dipole-dipole which is stronger than induced dipole-dipole forces that the alkanes have (haloalkanes also have induced),
Why do the boiling points of haloalkanes increase as you go down group 7?
Because the amount of electrons in the halogen increases which makes the permanent dipole larger and so the force strong and it is harder to break
What is a nucleophile?
It has a lone pair of electrons which are attracted to an electron deficient carbon atom
What is the charge on electron deficient carbon atoms?
Positive
What are the conditions for nucleophilic substitution?
The substances must be dissolved, some in water and haloalkanes have to be dissolved in ethanol as they are non-polar,
You also heat the reaction under reflux to increase the rate
What happens during nucleophilic substitution?
The nucleophile (often OH-) is attracted to the slightly positive charge of the carbon that the halogen is bonded to in a haloalkane, it will form a bond with the carbon and the electrons pair between the alkane and carbon will move to the alkane and it will leave- making an alcohol and a free radical which will bond to the whatever was bonded to the OH-)
How does nucleophilic substitution work with ammonia?
The ammonia is attracted to the positive carbon and kicks the alkane off, the NH3 is now on the hydrocarbon but the N has a slight positive charge so another NH3 attracts one of the hydrogens which leaves its electrons with the N on the carbon chain so it forms and amine and the H leaves to for NH4 and then bond with the halogen that left earlier
What happens in nucleophilic substitution with cyanide?
The cyanide free radical bonds with a carbon and kicks of the halogen attached to it, creating a nitril and a free radical that bonds with whatever the cyanide was bonded to before
What happens in an elimination reaction?
OH- attracts a hydrogen from a haloalkane, the electron pair moves towards the carbon and forms a double bond with the carbon next to it, this kicks of the halogen on that carbon as it cant have more than 4 double bonds, it forms and alkene, water and the halogen bonded with what the OH- was initially with
What is ozone
O3 and it is in our stratosphere
How does ozone protect us?
Oxygen absorbs uv light from the sun which breaks it into two oxygen free radicals, one of these can then bond to another oxygen molecule (using uv again) to form O3 (ozone) and can be broken back in a reversible reaction, all the use of uv radiation protects too much from getting to us
