Chapter 5

Question 1

Alkenes

Answer 1

At least a a double bound

Also called unsaturated hydrocarbon

Question 2

Degree of unsaturation

Answer 2

How many H2 are missing

+1 to the degree for every double bond and ring

Question 3

Nomenclature alkenes

Answer 3

Look for longuets chain with double bond and give it lowest number

Hydroxyl group has priority over double bond

2 double bonds= (name)diene

(Name)triene

Etcp

Question 4

Vinyl of carbon

Answer 4

Sp2 carbon of an alkene

Question 5

Allylic carbon

Answer 5

Adjacent to vinylic carbon

Question 6

Addition reaction

Answer 6

Alkenes reacting with HX (x halogen) = alkyl halide

Breaks double bond and halogen attaches to where it used to be

Question 7

Électrophiles

Answer 7

Attracted to electrons, to negative charges
Have a positive charges or an incomplete octet

Question 8

Nucleophiles

Answer 8

Attracted to positive charges
Have electron pairs to share
Have a negative charge
Have a pi bond

Question 9

Electrophile addition to an alkene

Answer 9

Step 1:carbocation (electrophile (ex hydrogen) attaches to nucleophile (curved arrow from alkene double bond to electrophile, arrow from hydrogen to halogen). Nucleophile becomes electrophile and other part of electrophile becomes nucleophile)(slow endergonic reaction)
Step 2:alkyl halide(fast fast exergonic)

Question 10

Réaction coordinate diagrams

Answer 10

Free energy on y axis

Free energy is low on reactants and products side
Transition state (middle) has a lot of free energy where bonds are partially broken (dotted lines)

Number of transition states (peaks) is number of elementary steps

Slow enderginic reaction : reactants lower than products, not spontaneous, delete G positive . Possible to occur if linked to exergonic 2nd step h coupled reactions), equilibrium arrows towards reactants

Fast exergonic: reactants high than products, spontaneous, negative delta G, equilibrium arrows towards products

Question 11

Catalyst hydrogenation

Answer 11

Addition of alkene and H2

Above arrow there is Pd/C (catalyst) or Pt/C

Breaks dédouble bond and Produces alkanes

Hydrogen and pi bond adsorbed (stuck to surface of catalyst) and then they bond to the carbons. Addition of hydrogen is a cis addition (desorbtion ) (hydrogens are added on the same side of the two carbons)

Question 12

Stability of alkenes number of hydrogens

Answer 12

No matter constitutional isomer of alkene, hydrogenation leads to same product

Most unstable alkene will produce the greatest changea in delta h when hydrogenated

More R groups on doruble bond means more stable
More hydrogens on double bond means least stable

Question 13

Stability of alkene: cis and trans

Answer 13

Trans is more stable than cis alkene

Higher delta h (lower heat of hydrogenation) means more stable isomer

Cis alkane as unstable as alkane with 2 same group on same side

Question 14

Electrophilic additions

Answer 14

Électrophile and nucleaophile added to alkenes

Question 15

Carbon preferred alkyl halide

Answer 15

Tert- carbocataion more stable so will form more

Because more stable so Lower activation energy

Hyporconjugation also stabilized carbocation

Question 16

Energy diagram

Answer 16

Similar energy, Similar looking structures

Exerginic reaction transition state ressembles more reactant (closer in energy) and inverse

More stable carbocation is formed more rapidly and has more amounts of productsi

Question 17

Markovniks rule

Answer 17

Hydrogen adds to the carbon with the most hydrogens

Question 18

Regioselective réactions

Answer 18

Produce more of one constitutional isomer than another (has a major product)

Can be moderately, highly or completly regioselectivd (all of major) depending of the difference of stability of the carbocations

Reaction can also be not regioselective if equal amounts of isomers (only if carbocations are equal stability)

Question 19

Acid catalyze addition of water

Answer 19

H2O added to alkene

Hydrogen attached to 1 carbon and OH to other carbon