2 chiral centres cancel each other out to create an optically inactive molecule Achiral 2 N (n=number of chiral centres) They have a plane of symmetry that divides them into mirror images of each other
A diastereomer that differs at only 1 chiral center Same molecular formula/bond connectivity (different compound, no mirror images).
Ring closure forms at epimeric carbon New diastereomer Same molecular formula/bond connectivity (different compound, no mirror images). Orientation of substituent - e.g. alpha and beta glucose
What are the physical properties of alkanes?
oil on water insoluble in water, waxy, lowest density of all organic compounds Soluble in other hydrocarbons eg. benzene, chloroform
What governs boiling point?
IMF ⇒ as carbons are added to chain, molecular weight increased ⇒ IMF++ ⇒ ncreased BP ++
cyclohexane = 0 ring strain; ++ as rings get bigger or smaller
What is the impact of Ring Strain on molecule?
Increased ++ Energy means less stable and more reactive
What shapes do cyclohexanes exist in?
Chair, boat, twist at room temp
Which cyclohexane is the most common?
Chair is at the lowest energy is the most stable Twist boat is usually intended.
Where are the hydrogens in cyclohexane?
In chair shape H’s can are in equatorial or axial hydrogens
H’s project up and down, axis of evil Can cause crowding ⇒ leads to steric hindrance Large substituents in the axial position ⇒ require more energy, less stable
Which shape do cyclohexanes favour?
Most substituent positions favour: equatorial position ⇒ to reduce steric hindrance crowding. H's like to travel to the Equator.
Another name for alkanes?
What do alkanes react with?
:-) w/energy they will combust with oxygen in radical rx (hate::-( acids, bases, most reagents)
What are the products of oxygen combustion?
carbon dioxide, water and heat
What is the heat of combustion?
Change of enthalpy Can compare stabilities of isomers because it creates equal amounts of products.
What is Enthalpy?
a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume. the change in enthalpy associated with a particular chemical process.
(most to least) F - Cl-Br-I Frank reacted and CLobbered BrIan
What is the selectivity of halogens?
Opposite of Frank CLobbered Brian 5 :4: 1
What is reactivity?
Fluorine is the smallest atom of the halogen elements. It also has the strongest ability to attract electrons from other elements, making it the most reactive of the halogens. As you look down the column on the periodic table, the atoms get larger and have less ability to attract electrons.
What is the shape of alkyl radicals?
They exhibit trigonal planar geometry
An alkyl radial is ....
An alkyl radial is a radical that has the structural formula of an alkyl group.
Selectivity in OChem?
Is ... how choosy a halogen radical is when selecting its position on the alkane
What is Halogenation?
Alkane + halogen ⇒ in presence of heat/UV light to create a free radical.
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