General- Alkynes

Question 1

Describe the orbitals involved in the triple bond

Answer 1

The tripled bond is one sigma bond and 2 pi bonds
The sigma is formed from the end on overlap of the two sp orbitals from the carbons
The 2 pi bonds are formed from the side on overlap of 2 unhybridised p orbitals from each carbon (px & pz)
C-H sigma is from sp and s orbital

Question 2

What is the bond angle in the triple bond?

Answer 2

180 degrees

Question 3

What hybridisation are the carbon atoms

Answer 3

Sp as they are each bonded to two atoms

Question 4

How can you name alkynes?

Answer 4

1) select the longest continuous chain and add yne

2) triple bond is lowest carbon

Question 5

How is ethyne made and what is its use?

Answer 5

2CH4 to ethyne and H2
1200 degrees
Steam

Ethyne is an industrial feedstock

Question 6

What is the acidity of terminal alkynes?

Answer 6

They are weak acids

Need a strong base

Question 7

What is the order of acidity for alkynes, alkenes and alkanes?

Answer 7

Alkynes> alkenes> alkanes

Question 8

Why is this order of acidity observed?

Answer 8

Alkynes are more acidic as they have greater s character in the bonds
This means the anions are more stable which is energetically favourable
Alkanes (sp3), alkenes (sp2)

Question 9

Do alkenes, alkynes or alkanes have the strongest bond?

Answer 9

Alkynes have shorter and stronger bonds

They have more covalent bonds that hold carbons together