3.3 Halogenoalkanes Flashcards

1
Q

Are halogenoalkanes soluble in water?

A

Insoluble as C-H bonds are non-polar, not compensated for enough by C-X bond polarity

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2
Q

Do halogenoalkanes have a polar bond? Why?

A

Yes polar, as hydrogen has a higher electronegativity than C

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3
Q

Which intermolecular forces do they have? Why?

A

Permanent dipole-dipole and van de Waals forces of attraction
C-X bond polarity creates permanent dipoles

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4
Q

When would they have higher boiling points?

A

Increase Carbon chain length
Halogen further down group 7

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5
Q

How would the mass of a halogenoalkane compare with the mass of an alkane of the same chain length?

A

Greater as mass of halogen > mass of H

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6
Q

What is the most important factor in determining their reactivity?

A

Carbon-Halogen bond polarity

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7
Q

What is the order of reactivity of halogenoalkanes?

A

Although C-F is the most polar bond, the bond enthalpy of C-X decreases down the group, so reactivity increases down the group

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8
Q

What is a nucleophile?

A

A negatively charged ion with a lone pair of electrons which can be donated to an electron deficient atom

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9
Q

Give 3 examples of nucleophiles

A

:OH-
:CN-
:NH3

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10
Q

What is nucleophilic substitution?

A

A reaction where a nucleophile donates a lone pair of electrons to a δ+ C atom, δ- atom leaves molecule

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11
Q

What are CFC’s?

A

Chlorine-fluoro-carbons - halogenoalkanes containing C, F and Cl only (No H)

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12
Q

What is the problem with CFC’s

A

Although unreactive under normal conditions, they catalyse the breakdown of ozone in the atmosphere via free radical substitution

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13
Q

What are CFC’s being replaced with?

A

HCFCs ( Hydrogen, Chlorine, Fluorine, Carbon)
HFC’s ( Hydrogen, Fluorine, Carbon)

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14
Q

What are the conditions / reactants needed for the elimination reaction of halogenoalkanes

A

NaOH or KOH dissolved in ethanol (no water present)
Heated

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15
Q

What is formed in the elimination reactions of halogenoalkanes?

A

An alkene, water and halogen ion

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