Chapter 14 - Alkenes Flashcards
What are Sigma Bonds and how are they created?
Give an example of where Sigma bonds may be?
What are the Sigma Bond angles?
Freely rotational bonds created by overlapping orbitals
Covalent bonds in a Hydrocarbon
Tetrahedral, 109.5 degrees
What is the structure of an Alkene?
- Unsaturated Hydrocarbon with double covalent bonds with the general formula CnH2n+1
- Planar with 3 bonding regions where bonds move as far apart, 120 degrees bond angles
- Alkenes identified by Orange Bromine becoming Colorless
- Insoluble in water
What are Pi bonds?
Where could pi bonds be located?
Why cant Pi bonds rotate?
Restricted Rotational covalent bonds created by Orbitals overlapping sideways, above and below a sigma bond
In C = C bonds, between P-Orbitals in an Alkene
Rotating reduces the overlap, removing the Pi bond
What is electrophilic addition?
A mechanism involving an electrophile invading the electrons in a pi bond, within an Alkene
What is an electrophiles?
Examples of Electrophiles?
Electron Pair Acceptors, that is a positively charged ion or has a positively charged region
Br2, HBr, H2SO4, H3PO4
Outline Electrophilic Addition involving Br2
When Br2 is near the double bond, electrons in the double bond pushes the electrons on Br2 creating an induced dipole
Electrons in the double bond attract the partial +Br, where the electrons on the Br2 move onto the -Br, creating a new bond, removing the double bond and creating a Br ion
A carbocation is formed as a Carbon has a lone pair of electrons, Br ion is attracted to the Carbocation forming a haloalkane
Summary: Forms a haloalkane with 2 halogens
Outline Electrophilic Addition involving HBr
HBr (H is positive) is already dipole due to electronegativity.
Electrons from Alkene attract the H+ and created a -Br ion
Carbocation is formed, -Br ion attracted to the Carbocation forming a Haloalkane
What are the Conditions needed for Electrophilic Addition involving H2SO4
Outline Electrophilic Addition involving H2SO4
Cold Concentrated H2SO4
H-OHSO3, +H and -OHSO3
Electrons in Alkene attract the H+ forming a carbocation and the -HSO4 attracts to the carbocation creating a (Alkyl)hydrogen Sulfate
What could happen to the carbocation during electrophilic addition with HBr or BR2?
How do you identify a major/minor carbocation
Major/Minor Products made, Major product being the one being more likely to be made
Depending on the Alkyl groups attached to the C-X, more Alkyl groups attached to it, the more stable it is. A secondary carbocation would be more stable than a primary carbocation for example.
Conditions needed for Electrophilic Addition involving H3PO4 (in water)
What mechanism does this partake in
Catalyst (H3PO4), 70atm Pressure, 300 Degrees, Silica Support
Electrophilic Addition
Outline Electrophilic Addition involving H3PO4 (in water)
Electrons in Double bond attract the the H+ in +H-(-H2PO4) forming a carbocation
Carbocation then reacts with H20 creating an alcohol and a catalyst (H+ from the H2O) to repeat the process
What is Direct Hydration?
Example of Direct Hydration?
Adding water to an alkene in presence of an acid to form an Alcohol
Electrophilic Addition with H3PO4 in water
How can we dehydrate an Alcohol/Dehydrogenation?
What is Dehydrogenation an example of (What mechanism)?
Using H3PO4 or H2SO4 to remove Alcohol to create Alkenes
Elimination Reaction
What are addition polymers?
What is the process of the formation of Polymers?
What are the conditions needed for Polymerization?
Polymers made of monomers (Alkenes)
Polymerization, formation of polymers from monomers
High Pressure/Temperature, Catalyst
How do alkenes form polymers?
What is the name of an addition polymer?
Their double bond opens up to join another monomer
Poly(Alkene) e.g. Poly(Chlorobutene)
