Alkynes

Question 1

Alkynes

Answer 1

Unsaturated hydrocarbons
Contain Carbon-Carbon triple bonds
General formula CnH2n+2

Question 2

Naming Alkynes (IUPAC)

Answer 2

Find the longest carbon chain (draw a line through it) that includes the triple bond

Name from the longest chain (root name) indicating the position(s) of the triple bond

Question 3

Alkynes prefer

Answer 3

Trans over cis

Question 4

Summary

Answer 4

Alkanes: Structure, nomenclature, physical properties (solubility, boiling point), chemical reactions (combustion, halogenation)

Alkenes: structure, nomenclature, chemical reactions (electriphilic addition - mechanisms with curly arrows)

Alkynes: structure, nomenclature, chemical reactions (electrophilic addition of one and two equivalents of reagents)

Question 5

Boning in Alkanes, Alkenes and Alkynes

Answer 5

Methane has 4 covalent C-H bonds

All four bonds have the same length and all bond angles are the same (109.5°)

(Remember hybridisation)
-mixing atomic orbitals to form hybrid orbitals

Question 6

Orbitals that hybridise in methane

Answer 6

2s, 2px, 2py, 2pz orbitals
Four

Question 7

Hydrogen atoms overlapping with carbon sp3 orbitals

Answer 7

Form methane

Question 8

NB

Answer 8

Any carbon atom bonded to 4 other atoms is sp3 hybridised

Question 9

Binding in ethane

Answer 9

The two carbon atoms in ethane are tetrahedral. Each carbon uses four sp3 orbitals to form four covalent bonds

Question 10

One sp3 orbital of one carbon

Answer 10

Overlaps with an sp3 orbitals of the other carbon to for the C-C bond

Question 11

Each of the remaining sp3 orbitals

Question 12

Bonding in Ethene

Answer 12

Each of the carbon atoms in Ethene forms four bonds, but each carbon is bonded to 3 atoms

Question 13

The geometry around the carbon is

Answer 13

Trigonal planar, and that bond angles are all close to 120°

Question 14

To bond to three atoms,

Answer 14

Each carbon hybridises 3 atomic orbitals; an s orbitals and two of the p orbitals

Question 15

After hybridisation

Answer 15

Each carbon has three sp2 orbitals and one unhybridised p orbital

Question 16

Pne carbon-carbon bond is a

Answer 16

Sigma bonded formed by sp2-sp2 overlap

Question 17

The second carbon-carbon bond is

Answer 17

A pi bond formed by the side-side overlap of a p orbital of one carbon with a p orbital of the other carbon

Question 18

The C-H bonds

Answer 18

Are sigma bonds formed by sp2-s overlap

Question 19

Bonding on ethyne

Answer 19

Each of the carbon atoms in ethyne forms four bonds, but each carbon is bonded to two atoms

Question 20

The geometry around the carbon is

Answer 20

Linear

Question 21

To bind to two atoms

Answer 21

Each carbon hybridises two atomic orbitals; an s orbital and a p orbital

Question 23

Alkynes often react by

Answer 23

Electrophilic addition reactions

Question 24

Most of the addition reactions of alkenes

Answer 24

Also occur for Alkynes

Question 25

But now there are