Ch 5- Alkenes

Question 1

unsaturated hydrocarbon

Answer 1

hydrocarbon that contains one or more C=C double or triple bonds

Question 2

The three most important classes of unsaturated hydrocarbons are _____.

Answer 2

alkenes, alkynes, and arenes

Question 3

aryl group

Answer 3

a group derived from an arene by removal of an H

Question 4

phenyl group

Answer 4

a group derived by removing an H from benzene

Question 5

index of hydrogen deficiency

Answer 5

the sum of the number of rings and pi bonds in a molecule; (H_ref - H_molecule)/2 where H_ref is the number of hydrogens in a reference alkane of the same number of carbon atoms

Question 6

A C-C double bond consists of one ______ bond and one _____ bond.

Answer 6

sigma; pi

Question 7

Each carbon of the double bond uses its three ___ orbitals to form ____ to ____ atoms. The unhybridized ___ orbitals, which lie ___ combine to form 2 ___, one ____ and the other ___.

Answer 7

sp2 hybrid; sigma bonds; 3; 2p; perpendicular to the plane created by the axes of the 3 sp2 hybrid orbitals; pi molecular orbitals; bonding; antibonding

Question 8

cis, trans isomers

Answer 8

isomers that have the same order of attachment of their atoms but a different arrangement of their atoms in space owing to the presence of either a ring or a C=C double bond

Question 9

Any alkene in which each carbon of the double bond has 2 different groups bonded to it shows cis, trans isomerism because of ___.

Answer 9

restricted rotation about the double bond

Question 10

Cis alkenes with double bonds in open chains are ___ (more/less) stable than their trans isomers because of ___.

Answer 10

less; steric strain between alkyl substituents on the same side of the double bond

Question 11

What is the first step in naming an alkene?

Answer 11

Number the longest carbon chain that contains the double bond in the direction that gives the carbon atom of the double bond the lowest possible numbers

Question 12

After naming the longest carbon chain of the alkene, what is the second step in naming?

Answer 12

Indicate the location of the double bond by the number of its first carbon

Question 13

After naming the longest chain and indicating the location of the double bond, what is the third step in naming?

Answer 13

Name the substituents and number themmmmm

Question 14

cis alkene

Answer 14

refers to molecules in which the carbon atoms of the main chain are on the same side of the double bond

Question 15

trans alekne

Answer 15

refers to molecules in which the carbon atoms of the main chain are on opposite sides of the double bond

Question 16

E

Answer 16

specifies that groups of higher priority on the carbons of a double bond are on opposite sides (EPPOSITE)

Question 17

Z

Answer 17

specifies that groups of higher priority on the carbons of a double bond are on the same side (ZAME ZIDE)

Question 18

What is the smallest stable trans cycloalkene?

Answer 18

trans cyclooctene

Question 19

A double bond at a bridgehead alkene imparts considerable strain on the molecule because ___.

Answer 19

the alkene cannot be planar while the rest of the carbons in the bicyclic system span the rings

Question 20

For alkenes containing two or more double bonds, the infix -en- is changed to ___.

Answer 20

-adien-, -atrien-, etc.

Question 21

polyene

Answer 21

an alkene containing two or more double bonds

Question 22

For an alkene with n C=C double bonds, how many stereoisomers are possible?

Answer 22

2^n

Question 23

What are the only attractive forces between alkene molecules?

Answer 23

dispersion forces

Question 24

Two, three, and four carbon alkenes are ___(solid, liquid, gas) at room temp.

Answer 24

gas

Question 25

Alkenes are ___ (soluble/insoluble) in water.

Answer 25

insoluble

Question 26

terpene

Answer 26

a compound whose carbon skeleton can be divided into two or more units identical with the carbon skeleton of isoprene

Question 27

What is the IUPAC name for isoprene?

Answer 27

2-methyl-1,3-butadiene