13. Halogenoalkanes

Question 1

What is a haloalkane?

Answer 1

• Are similar to alkanes but with one or more of the hydrogen atoms replaced by a halogen

Answer 2

• They can contain more than one type of halogen
• E.g. CFCs (chlorofluorocarbons) contain both chlorine and fluorine atoms

Answer 3

• Some haloalkanes are useful themselves but many are valuable intermediates in the production of other molecules

Answer 4

• Fluorine - fluoro-
• Chlorine - chloro-
• Bromine - bromo-
• Iodine - - iodo

number of halogens
one -
two - di
three - tri
four - tetra
five - penta

• listed alphabetically

Answer 5

• Halogenoalkanes can be classified as primary, secondary or tertiary depending on the number of carbon atoms attached to the C-X functional group.

Question 6

A

Answer 6

• A chain of carbon atoms can be represented by R when drawing the structure. This is referred to as an R group

Question 7

Define a primary haloalkane

Answer 7

One carbon attached to the carbon atom adjoining the halogen
* One R group attached to the carbon linked to the halogen

Question 8

Define a secondary haloalkane

Answer 8

Two carbons attached to the carbon atom adjoining the halogen
* Two R group attached to the carbon linked to the halogen

Question 9

Define a tertiary haloalkane

Answer 9

Three carbons attached to the carbon atom adjoining the halogen
* Three R group attached to the carbon linked to the halogen

Question 10

Why are haloalkanes not soluble

Answer 10

no fluorine, oxygen or nitrogen

Question 11

What intermolecular forces are found in haloalkanes?

Answer 11

• difference in electonegativtiy between halogen and carbon = dipole dipole
• vanderwall

Answer 12

• Straight chain alkane has a higher b.p. than branched chain alkene with the same number of carbons. because as the branching increases surface area decreases and wander wall force decreases

Answer 13

Bond enthalpies
* The C-X bonds get weaker as you go down group
* Flourine is the smallest atom of the halogens so the shared electrons in the C-F bond are strongly attracted to the nucleus. This makes a strong bond
* Bond enthalpies let us predict that iodo-compouds are most reactive

Answer 14

• Halogen are more electronegative than carbon so the carbon bonded to the halogen has a partial positive charge - electron deficient
  ( It can be attaked by reagaents that are electron rich- these are called nucleophiles
• The more polar the bond, the more reactive the haloalkanes as the C delta+ has the highest positive charge and is most easily attacked by a nuecleophiel

Answer 15

• Reactivity of haloalkeans
• When haloalkanes react, it is almost always the C-X bond that breaks. There are two factors that determine how readily available the C-X bonds reacts