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Organic Chemistry 1 > Halogenoalkanes > Flashcards

Halogenoalkanes Flashcards

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1
Q

Why is the carbon-halogen bond polar?

A

Because there is a difference in electronegativity.

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2
Q

What is the relationship between the carbon-halogen bond polarity and the position of the halogen in group 7 (on the periodic table)?

A

The higher up the halogen is in group 7, the more polar the carbon-halogen bond is.

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3
Q

Are halogenoalkanes soluble in water?

A

No, because water forms hydrogen bonds whereas hydrogen only have permanent dipole-dipole forces and van der waals forces (which are weaker).

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4
Q

Describe and explain the relationship between chain length and boiling point for halogenoalkanes.

A

Longer chain halogenoalkanes have higher boiling points as they have more atoms, therefore more van der waals forces, which will take more energy to overcome.

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5
Q

Describe and explain the relationship between the position of the halogen in the group (on the periodic table) and boiling point for halogenoalkanes.

A

The higher the position of the halogen in the group, the lower the melting point because the molecule is smaller, therefore less van der waals forces, which take less energy to overcome.

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6
Q

What is a nucleophile?

A

An electron pair donor.

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7
Q

What is a substitution reaction?

A

A reaction where one functional group on a molecule is replaced by another.

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8
Q

What is the relationship between the bond enthalpy of the carbon-halogen bond and the position of the halogen in group 7 (on the periodic table)?

A

The higher the position of the halogen, the larger the bond enthalpy due to stronger bonds as there is a larger difference in electronegativity.

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9
Q

A halogenoalkane reacts with NaOH or KOH. What type of reaction is this? What is the name of the reaction mechanism?

A

This type of reaction is hydrolysis.
This reaction mechanism is nucleophilic substitution.

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10
Q

C2H5Cl + NaOH –> C2H5OH + NaCl

What are the conditions for this reaction?

A
  • Heat under reflux
  • NaOH (or KOH) dissolved in a 50/50 mix of ethanol/water
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11
Q

C2H5Cl + KCN –> C3H6N + KCl

What are the conditions for this reaction?

A
  • Heat under reflux
  • NaCN or KCN dissolved in ethanol (no water!)
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11
Q

A halogenoalkane reacts with NaCN or KCN. What is the name of this reaction mechanism?

A

Nucleophilic substitution.

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12
Q

What is the name of CN-

A

Cyanide ion

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12
Q

During the reaction of a halogenoalkane with cyanide ions, no water can be present. Why?

A

Otherwise OH- from H2O is substituted

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13
Q

A halogenoalkane reacts with cyanide ions. What is special about the product formed?

A

The carbon chain length is increased

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14
Q

A halogenoalkane reacts with excess ammonia. What is the name of this reaction mechanism?

A

Nucleophilic substitution.

15
Q

What are the conditions for reacting a halogenoalkane with ammonia?

A
  • In ethanol
  • Concentrated ammonia
  • In a sealed tube under high pressure + temperature
16
Q

What is interesting about the products of a reacting halogenoalkanes and ammonia?

A

You get a mixture of products (primary amines, secondary amines, tertiary amines..)

17
Q

How do you favour certain products when reacting halogenoalkanes and ammonia?

A

Having excess ammonia will favour primary amines.
Having excess halogenoalkanes will favour quaternary amines.

18
Q

What is a base?

A

A proton acceptor.

19
Q

What happens in an elimination reaction?

A

2 parts of a molecule are removed.

20
Q

C2H5Cl + NaOH –> C2H4 + NaCl + H2O

What is the name of this reaction mechanism?

A

Elimination.

21
Q

For an elimination reaction, involving reacting a halogenoalkane with NaOH. What are the conditions?

A
  • Heat under reflux
  • Only in ethanol (no water!)
  • Concentrated NaOH
22
Q

What is interesting about the products formed in an elimination reaction between NaOH and a halogenoalkane?

A

Different positional isomers are produced depending on where the hydrogen is removed from.

Organic Chemistry 1 (6 decks)

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