4.1.2

?
What are alkanes?
Saturated hydrocarbons containing single C–C and C–H bonds, as σ-bonds; can freely rotate.
1 of 9
What are σ-bonds?
The overlap of orbitals directly between the bonding atoms.
2 of 9
Explain the tetrahedral shape and bond angle around each carbon atom in alkanes, in terms of electron pair repulsion.
Each carbon atom is surrounded by 4 electron pairs in 4 σ-bonds; repulsion between electron pairs results in the shape; bond angle of 109.5
3 of 9
Explain the variations in boiling points of alkanes with different carbon-chain length and branching, in terms of induced dipole–dipole interactions (London forces).
As chain length increases, the molecules have a larger surface area, so more surface contact is possible between molecules, so Greater London forces; fewer surface points of contact between molecules with branches, so fewer London forces.
4 of 9
Explain the low reactivity of alkanes with many reagents, in terms of the high bond enthalpy and very low polarity of the σ-bonds present.
C-C and C-H σ-bonds are strong, C-C bonds are non-polar, C-H bonds can be considered non-polar.
5 of 9
Explain the complete combustion of alkanes, and the incomplete combustion of alkane fuels in a limited supply of oxygen.
In lots of oxygen, alkanes burning produces carbon dioxide and water; however in a limited supply of oxygen, combustion will produce water and carbon monoxide or soot.
6 of 9
Why is carbon monoxide dangerous?
CO is a colourless, odourless and highly toxic gas; it combines with haemoglobin to prevent the haemoglobin from transporting oxygen around the body.
7 of 9
How do alkanes react with chlorine and bromine?
By radical substitution using UV radiation; mechanism for this reaction needed (initiation, propagation and termination).
8 of 9
What are the limitations of radical substitution in synthesis?
Further substitution and reactions at different positions in a carbon chain.
9 of 9

Other cards in this set

Card 2

Front

What are σ-bonds?

Back

The overlap of orbitals directly between the bonding atoms.

Card 3

Front

Explain the tetrahedral shape and bond angle around each carbon atom in alkanes, in terms of electron pair repulsion.

Back

Preview of the front of card 3

Card 4

Front

Explain the variations in boiling points of alkanes with different carbon-chain length and branching, in terms of induced dipole–dipole interactions (London forces).

Back

Preview of the front of card 4

Card 5

Front

Explain the low reactivity of alkanes with many reagents, in terms of the high bond enthalpy and very low polarity of the σ-bonds present.

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Alkanes resources »