Exam 2

Question 1

Alkenes are also called olefins, meaning _______________

Answer 1

Oil forming gas

Question 2

Sigma bonds around the double-bonded carbon are ____ hybridized. Their angles are approximately _____ and the molecular geometry is _____ ______

Answer 2

Sp2
120º
trigonal planar

Question 3

Do double bonds have longer or shorter bonds compared to single bonds?

Answer 3

shorter

Question 4

Are alkanes saturated or unsaturated?

Answer 4

saturated (can’t add more)

Question 5

Are alkenes saturated or unsaturated?

Answer 5

unsaturated (deficient in hydrogens)

Question 6

What are the elements of unsaturation?

Answer 6

double bonds and rings

Question 7

What is the formula for unsaturation

Answer 7

2(#C)+2+(#N)-(#X)-(#H)/2

*oxygen is not included in equation at all!

Question 8

Methylene group

Answer 8

=CH2

Question 9

Vinyl group

Answer 9

-CH=CH2

Question 10

Allyl group

Answer 10

-CH2-CH=CH2

Question 11

Phenyl group

Answer 11

6 carbon ring with 3 double bonds

Question 12

Is cis or trans more stable in a cycloalkene?

Answer 12

cis

Question 13

trans cycloalkenes are not stable unless the ring has at least ___ carbon

Answer 13

8

Question 14

E-Z nomenclature (split double bond to determine)

Answer 14

if the high-priority groups are on the same side, they are Z

opposite sides, they are E

Question 15

What are some commercial uses of ethylene?

Answer 15

-polyethylene (plastic)
-acetic acid (cleaning/vinegar)
-ethylene oxide (epoxy)
-ethylene glycol (preservative)
-ethanol
-vinyl chloride (floor)

Question 16

What are some commercial uses of propylene?

Answer 16

-isopropyl alcohol and acetone

Question 17

What is polymerizing?

Answer 17

Adding the same monomer over and over again
(breaking the double bond and adding monomer)

Question 18

What are the properties of Alekenes?

Answer 18

-Cis has higher boiling and melting points than trans
-Cis have a greater dipole moment so they will be slightly polar
-branched have a lower boiling point
-less dense than water (sink)
-low boiling points that increase with mass

Question 19

higher number of carbon, _________ boiling point

Answer 19

higher

Question 20

Heat of hydrogenation

Answer 20

alkene + H2 -> alkane + heat
- double bond is broken up and hydrogens are added to fill the octet

Question 21

For the heat of hydrogenation, the higher the change in heat means the _____ stable and _____ reactive

Answer 21

more; less

vice versa

Question 22

For the heat of hydrogenation, the _____ substituted the double bond, the lower its heat of hydrogenation

Answer 22

more

Question 23

In cycloalkenes, ____ isomers are more stable

Answer 23

Cis

Question 24

In cycloalkenes, to form a stable trans double bond you must have ___ carbons

Answer 24

8

Question 25

Bredt's Rule

Answer 25

A bridged, bicyclic compound cannot have a double bond at a bridgehead position unless one of the rings contains at least 8 carbons

Question 26

E1 reaction

Answer 26

lose a hydrogen and a halide to form a double bond -unimolecular -2 steps -weak base -form a carbocation -carbocation formation is the rate-determining step -Zaitsev product

Question 27

Zaitsev's Rule

Answer 27

if more than one elimination product is possible, the most substituted alkene is the major product and is the most stable

Question 28

E2 Reactions

Answer 28

lose a hydrogen and a halide to form a double bond -bimolecular -one step (transition state) -strong base -Zaitsev product

Question 29

What is the order of reactivity for alkyl halides?

Answer 29

3º>2º>1º

Question 30

What happens if there is a bulky base in an E2 reaction?

Answer 30

They form Hofmann products

Question 31

Hoffman products

Answer 31

states that the less substituted will be the major product (opposite of Zaitsev's)

Question 32

What is the stereochemistry of an E2 reaction

Answer 32

anti-coplanar -the halide and proton must be 180º in Newman projection -this minimizes steric hindrance between the base and leaving group

Question 33

Dehydration of Alcohols

Answer 33

The removal of a H2O molecule -must have H2SO4 or H3PO4 and heat -E1 mechanism -obeys Zaitsev's rule

Question 34

Catalytic cracking of alkanes

Answer 34

A long-chain alkane is heated with a catalyst to produce an alkene and a shorter alkane -when you add H (hydrocracking); you only get alkanes

Question 35

Dehydrogenation of alkanes

Answer 35

the removal of an H2 from a molecule, forming a double bond

Question 36

Electrophilic addition

Answer 36

double bond attacks the electrophile creating a carbocation; nucleophile attacks and creates all single bonds

Question 37

Addition of HX

Answer 37

breaking a double bond, creating a carbocation; H and halide attach -the reverse of an E1 reaction

Question 38

Markovnikov's rule

Answer 38

the addition of a proton to the double bond of an alkene results in a product with the proton bonded to the carbon atom that already holds the greater number of hydrogens - to generate the most stable intermediate -carbocation 3º>2º>1º

Question 39

Free radical addition of HBr

Answer 39

forms an anti-Markovnikov product -add your Br to the carbon with the most hydrogens and the radical on the other carbon

Question 40

Hydration of alkenes

Answer 40

addition of water to the double bond to form an alcohol -reverse of the dehydration of alcohol -uses H2SO4 or H3PO4 -follows Markovnikov's rule -possible rearrangements

Question 41

Strong nucleophiles or bases promote ___ and ____ reactions

Answer 41

Sn2 or E2

Question 42

Primary halides usually undergo ___ reactions

Answer 42

Sn2

Question 43

Tertiary halides are a mixture of ____, ____, and ____. They cannot undergo ____.

Answer 43

Sn1, E1 and E2 Sn2

Question 44

High temperatures favor

Answer 44

elimination

Question 45

bulky bases favor

Answer 45

elimination