Report: Alkenes and Cycloalkenes

Question 1

They react with hydrogen gas to increase the number of hydrogen atoms to become alkanes, which are

Answer 1

saturated hydrocarbons

Question 2

do not contain the maximum number of hydrogen atoms.

Answer 2

unsaturated hydrocarbons

Question 3

Alkenes contain one or more
carbon–carbon double bonds that form when adjacent carbon atoms share _____.

Answer 3

two pairs of valence electrons

Question 4

In alkenes, the molecule is ____ because the carbon and hydrogen atoms all lie in the same plane.

Answer 4

flat or planar

Question 5

They result from combinations of orbitals within a given atom, either prior to or as bonding with another atom takes place.

Answer 5

hybrid orbitals

Question 6

They result from combinations of orbitals between atoms as bonding takes place to form molecules.

Answer 6

molecular orbitals

Question 7

When carbon connected to three other things, that is one of the bonds is a ____

Answer 7

double bond

Question 8

the molecule is modeled by combining the 2s and two of the 2p orbitals to produce

Answer 8

sp2 orbitals

Question 9

The sp2 orbitals are arranged in
a trigonal planar shape around
the central carbon atom, with bond
angles of

Answer 9

120 degrees

Question 10

The unhybridized p orbital is _____ to the plane.

Answer 10

perpendicular

Question 11

End-on-end overlap of the
sp2 orbitals to make a

Answer 11

sigma bond

Question 12

side-to-side overlap of the unhybridized p orbitals to make
a

Answer 12

pi-bond

Question 13

Because of the _____, free
rotation is not possible around
carbon-carbon double bonds.

Answer 13

pi-bond

Question 14

Alkenes also form ______. Because rotation around a multiple bonds is restricted, groups attached to the double‐bonded carbon atoms always remain in the same relative positions. These “locked” positions allow chemists to identify various isomers from the substituents’ locations.

Answer 14

stereoisomers

Question 15

are molecules with the same connectivity of atoms. They feature same side groups placed on the same side of a double bond.

Answer 15

cis-isomers

Question 16

feature molecules with the same side groups placed on opposite sides of a double bond.

Answer 16

trans-isomers

Question 17

Alkenes substituents are called ____ - a noncyclic hydrocarbon substituent in which a C-C double bond is present.

Answer 17

alkenyl groups

Question 18

most frequently encountered alkenyl groups

Answer 18

–Methylidene (one-carbon)- Common name: methylene
–Ethenyl (two-carbon)
Common name: vinyl
–2-propenyl (three-carbon) Common name: allyl

Question 19

The first three members of the alkene group are ____ in nature, the next fourteen members are liquids and the remaining alkenes are ___.

Answer 19

gaseous; solids

Question 20

Alkenes are soluble in nonpolar solvents such as ___

Answer 20

benzene and ligroin

Question 21

which has a lower melting point? cis-isomer or trans-isomer

Answer 21

cis-isomer: trans-isomers are packed in a U-bending shape

Question 22

___ is more reactive than ___ due to the presence of ____

Answer 22

alkenes; alkanes; double bonds

Question 23

The ____ which make up the double bonds can easily be removed or added as they are weakly held.

Answer 23

π electrons

Question 24

examples of naturally occuring alkenes

Answer 24

• ethene (produced by all higher plants)
• pheromone (insects- to transmit a message)
• terpenes

Question 25

produced naturally by all higher plants from the amino acid methionine and is a plant growth
regulator. It causes trees to lose their leaves and stems to thicken.

Answer 25

ethene

Question 26

compound used by insects (and some animals) to transmit a message to other members of the same species.

Answer 26

pheromone

Question 27

organic compound whose carbon skeleton is composed of two or more 5-carbon isoprene structural units

Answer 27

terpenes

Question 28

other examples of alkenes

Answer 28

• propylene
• B-carotene
• a-Pinene

Question 29

produced primarily as a by-product of petroleum refining and of ethylene production by steam cracking of hydrocarbon feedstocks.

Answer 29

propylene

Question 30

the orange pigment that gives
carrots their color. It is an important dietary source of vitamin A and is thought to offer some protection against certain types of
cancer.

Answer 30

B-carotene

Question 31

an organic compound of the
terpene class. It is found in the oils of many species of many coniferous trees, notably the pine.

Answer 31

a-pinene

Question 32

Alkenes are generally prepared through ______, in which two atoms on adjacent carbon atoms are removed, resulting in the formation of a double bond.

Answer 32

β elimination reactions

Question 33

methods of how alkenes can be prepared

Answer 33

a. Dehydration of alcohols
b. Dehydrohalogenation of alkyl halides
c. Dehalogenation of alkanes

Question 34

a molecule of water is eliminated from an alcohol molecule by heating the alcohol in the presence of a strong mineral acid.

Answer 34

Dehydration of alcohols

Question 35

the dehydration of alcohol consists of 3 mechanisms. these are

Answer 35

1. Protonation of the alcohol.
2. Dissociation of the oxonium ion.
3. Deprotonation of the carbocation.

Question 36

This step is a simple acid‐base reaction, which results in the formation of an oxonium ion, a positively charged oxygen atom.

Answer 36

Protonation of alcohol

Question 37

produces a carbocation, which is a positively charged carbon atom and an unstable intermediate.

Answer 37

Dissociation of the oxonium ion

Question 38

This results in the hydrogen on the α carbon becoming very slightly acidic and capable of being removed as a proton in an acid‐base reaction.

Answer 38

Deprotonation of the carbocation

Question 39

• involves the loss of hydrogen and a halide from an alkyl halide (RX).
• normally accomplished by reacting the alkyl halide with a strong base, such as sodium ethoxide.

Answer 39

dehydrohalogenation of alkyl halides

Question 40

are alkane molecules that contain two halogen atoms on adjacent carbon atoms, and can form alkenes upon reaction with zinc.

Answer 40

vicinal halides (dehalogenation of alkanes)

Question 41

2 main reasons why alkenes are more reactive than alkanes

Answer 41

WEAK BOND
- Pi bond is a weak bond, unlike
sigma bond that isn’t easily
break.
ELECTRON DENSITY
- Alkenes attract electrons,
Alkane doesn’t attract
electrophile.

Question 42

the reaction typical of alkenes is ___

Answer 42

addition reaction

Question 43

4 types of addition reactions of alkenes

Answer 43

• hydrochlorination (hydrohalogenation)
• hydration
• bromination (halogenation)
• bromo(halo)hydrin formation

Question 44

the addition of HX or H20 to an alkene, hydrogen adds to the carbon of the double bond having the greater number of hydrogens,

Answer 44

Markovnikov’s Rule

Question 45

a reaction in which one direction of bond forming or bond breaking occurs in preference to all other directions.

Answer 45

Regioselective Reaction

Question 46

H atoms add to each of the carbon atoms in double bond of an alkene.

Answer 46

hydrogenation

Question 47

a large molecule that is consists of small repeating units called monomers.

Answer 47

monomers

Question 48

formation process of monomers by
repeated addition reactions of many unsaturated alkene molecules.

Answer 48

Addition polymerization

Question 49

is a method of oxidatively cleaving alkenes or alkynes using ozone (O3).

Answer 49

ozonolysis