Use of Curly Arrows in Mechanisms

Question 1

Free radical processes are also very important in biological systems. How do they occur?

Answer 1

They occur by one elctron redox processes + transition metals.

Question 2

How is the hydroxyl radical ( HO^. ) formed and where is it important?

Answer 2

Formed when water is irradicated (destroyed).

It’s important in biological reactions.

Question 3

Illustrate 3 examples of curly arrows in ionic (2e-) processes.

1. Neutralisation of a hydroxide ion by a proton
2. Substitution of haloalkane with hydroxide ion
3. Delocalisation of e-s within anions

Answer 3

1. Formation of water molecule = 2e- lone pairs from O attacks H+
2. Lone pair on HO^- attacks C on C-Br. Br ion takes the 2e-s in the bond b/w C-Br and becomes a stable Br atom.
3. Two resonate hybrids of carboxylate ions

Question 4

Neutralisation of a hydroxide ion by a proton.

What kind of curly arrow process is this?

Answer 4

Ionic.

Question 5

Substitution of haloalkane with hydroxide ion.

what kind of curly arrow process is this?

Answer 5

Ionic.

Question 6

Delocalisation of e-s within anions e.g. two resonate hybrids of carboxylate ions.

What kind of curly arrow procces is this?

Answer 6

Ionic.

Question 7

Show the neutralisation of a hydroxide ion by a proton (ionic process).

Answer 7

See notes in lecture 5 page 1.

Question 8

Show the substitution of haloalkane with hydroxide ion (ionic process).

Answer 8

See lecture 5 page 1.

Question 9

Show the delocalisation of e-s within anions e.g. two resonate hybrids of carboxylate ions (ionic process).

Answer 9

See lecture 5 page 1.

Question 10

How can you explain that the two C-O bonds (both double and single) are identical in length, rather than one long and one short one?

Answer 10

Delocalisation of electrons within the anions occurs.

Question 11

One way delocalisation of e-s in anions be important?

Answer 11

Two C-O bonds in carboxylate ions can have the same bond length despite having one single and one double bond.

Question 12

Draw a carboxylate ion.

Answer 12

See lecture 5 page 1.

Question 13

Show the 2 resonance states / hybrids of carboxylate ion.

Answer 13

See lecture 5 page 1.

Question 14

Show the ionic curly arrow mechanism of the delocalisation that occurs in carboxylate ion.

Answer 14

See lecutre 5 page 1.

Question 15

Explain the term delocalisation in terms of elctrons.

Answer 15

Delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond.

Question 16

How does delocalisation occur in organic chemistry?

Answer 16

In organic chemistry, this refers to resonance in conjugated systems and aromatic compounds.

Question 17

What is the molecular formula of carboxylate ion?

Answer 17

CH₃COO^-