LT#1&2: Alkenes, Alkynes, Cyclical and Aromatics

Question 1

What functional group does an Alkene have?

Answer 1

C=C

Question 2

Explain why Alkenes are described as being unsaturated.

Answer 2

When forming a double bond, 2 H’s must be removed. Each carbon is then not bonded to the maximum possible number of atoms

Question 3

What is the general formula for Alkenes?

Answer 3

CnH2n.

Question 4

What additional naming rules do you need to follow to indicate the double bond in an alkene?

Answer 4

1. Use the suffix “ene”
2. Double bonds must be included in the main chain and take numbering priority over alkyl groups.
3. Add the position # of the double bond in front of the suffix if there is more than 1 possible location.
4. If there is more than 1 double bond, list all the position #’s and place molecular prefix in front of “ene”.

Question 5

Describe the Melting Point of Alkenes.

Answer 5

The C=C makes the molecule smaller, which weakens LDs lowering MP compared to Alkanes.

Question 6

Describe the Solubility of Alkenes.

Answer 6

The C=C has no effect on solubility because it does not change the DID the water uses.

Therefore Alkenes have same solubility as Alkanes.

Question 7

What functional group do Alkynes have?

Answer 7

C to C triple bonds.

Question 8

Explain why Alkynes are described as being unsaturated.

Answer 8

When forming a triple bond, 4 H’s must be removed. Each carbon is then not bonded to the maximum possible number of atoms.

Question 9

What is the general formula for Alkynes?

Answer 9

CnH2n-2

Question 10

What additional naming rules do you need to follow to indicate the triple bond in an alkyne?

Answer 10

1. Use the suffix “yne”
2. Triple bonds must be included in the main chain and take numbering priority over alkyl groups.
3. Add the position # of the triple bond in front of the suffix if there is more than 1 possible location.
4. If there is more than 1 triple bond, list all the position #’s and place molecular prefix in front of “yne”.

Question 11

Describe the Melting Point of Alkynes.

Answer 11

The triple bond introduces a linear shape which increases the molecule’s surface area. This strengthens LDs, which increases MP compared to Alkanes.

Question 12

Describe the Solubility of Alkynes.

Answer 12

The C=C has no effect on solubility because it does not change the DID the water uses.

Therefore Alkynes have same solubility as Alkanes.

Question 13

Cyclical hydrocarbons contain..

Answer 13

Carbons in a ring

Question 14

What additional rules do you need to follow while naming a cyclical compound?

Answer 14

1. The ring is always your main chain.
2. Add “cyclo” in front of the root name.
3. You can start numbering C’s anywhere in the ring, and move either direction to get lowest possible numbers.
4. If double or triple bonds present, one must be between C-1 and C-2.

Question 15

What affect does the carbon ring have on the compound’s Melting Point?

Answer 15

Rings restrict bond rotation. This allows molecule to be easier to pack, so increases MP.

Question 16

What affect does the carbon ring have on the compound’s Solubility?

Answer 16

No Effect.

Question 17

What functional group do Aromatics have?

Answer 17

Contains a ring with resonance (1.5 bonds between carbons).

Question 18

How do you recognize an Aromatic Hydrocarbon from a structural diagram?

Answer 18

Circle drawn inside carbon ring.

Sometimes drawn as alternating single and double bonds around the ring.

Question 19

How do you represent Benzene in an expanded molecular formula?

Answer 19

C6H6 or C6H5 if something attached.

Question 20

Benzene is not the main chain in the molecule when…

What is a side chain benzene called?

Answer 20

attached to a chain with 7 or more carbons.

Phenyl Group