ALKYNES

ALKYNES-Characterized by C C triple bond(s)

-Classified as unsaturated hydrocarbons

-empirical formula = CnH2n-2

(applies when the molecule only has one triple bond)

CnH2n-2, n=5

= C5H8

ALKYNESProperties:-Are hydrophobic like all hydrocarbons

-Have higher boiling points than alkanes and alkenes due to their ability to stack

ALKYNESSome IUPAC names of alkynes:

All alkynes have the suffix “yne”

ethyne propyne but-1-yne

ALKyNESIUPAC naming system:

prefix suffix

Number of carbons in the longest chain

family

but yneEx:

-#-

Location number

-1-

ALKYNESIUPAC naming system:

Name the following alkynes:

hex-1-yne hex-3-yne

ALKYNESIUPAC naming system:

Name the following alkynes:

4-methylhex-2-yne 5-ethyl-4,6,7-trimethylnon-2-yne

1 2 3 4

5 61

23

456

7

89

The triple bond has a higher numbering priority than the alkyl and halide substituents

ALKYNESIUPAC naming system:

Name the following alkynes:

hex-4-en-1-yne 3-ethylhept-1-en-4-yne

Alkenes are ordered first in the name, and the “e” ending is dropped.

Generally, double bonds and triple bonds have equal numbering priority* (aim to get the lowest numbers).

1

23

4

5

6

1 2

3 4 5 6

7

ALKYNESIUPAC naming system:

Name the following alkynes:

hex-1-en-5-yne

1

2

3

4

5

6

hex-5-en-1-yneor

65

43

2

1

*Double bonds have higher priority than triple bonds whenever there is ambiguity in their numbers. This uses the rule where alpha-order is final tie-breaker like before.

ALKYNESIUPAC naming system:

Name the following alkynes:

cyclononyne cyclooct-1-en-4-yne

1

2

3

4 5

6

7

8

ALKYNESIUPAC naming system:

Name the following alkyne:

3,4,5-trichloro-8,9-diethyl-5,7,7-trifluorocyclononyne

12

3

4

5

67

8

9

FF

F

Cl

Cl

Cl

ALKYNESDrawing alkynes:

Draw the following alkynes using line diagrams

non-2-yne

6

5

4

3

2

1

7

8

9

The triple bond cannot bend, so the bonds adjacent to a triple bond must be straight.

non-1-yne

6

5

4

3

2

1

7

8

9

ALKYNESDrawing alkynes:

Draw the following alkynes using structural diagrams

4,5-dibromohex-2-yne

C

H

Br

C

H

H

HC C

H

Br

C

H

H

CH

1,2-dimethylcyclooct-1-en-4-yne

C

C C

C C

C

C HH

H

C

H

H

H

H

H

H

HC

C

HH

HH

ALKENESRECALL:

Name the following alkenes:

4-methylpenta-1,3-diene hepta-1,3,6-triene

When there is more than one double bond, add the letter “a” to the end of the prefix (i.e. buta)

ALKYNESMultiple Double Bonds AND/OR Triple Bonds:

octa-2,4-dien-6-yne

When there is more than one triple bond, AND a double bond, add the letter “e” to the end of the double bond sufix -ene

dec-1-ene-4,9-diyne

When there is more than one double bond AND a triple bond, add the letter “a” to the end of the prefix (i.e. buta)

nona-5-7-diene-1,3-diyne

ALKYNES

undeca-1,6,-diene-3,9-diyne