CD - Bonding and structure *01 Flashcards

1
Q

How do dyes attach themselves to fibres

A

intermolecular bonds, ionic bonds, covalent bonding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How do dyes attach themselves to fibres: Hydrogen bonds

A

functional groups enable dye to attach to fibres

- -NH2, amine group forms hydrogen bonds with fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What fibres do dyes that hydrogen bonds, bond well to?

A

cellulose, cotton, and linen as they contain loads of -OH groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Are dyes that hydrogen bond colourfast?

A

no

the hydrogen bonds arent strong enough

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do dyes attach themselves to fibres: ionic interaction

A
  1. acidic groups (carboxylic/sulfonic acid), help dyes bind to alkaline -NH- links in fibres
    - H+ ions move from dye to fibre molecule and ionic interactions hold them together

DYE-COOH + NH —> DYE-COO-+NH2

  1. some dyes have ionic salt groups (-SO3-Na+), these can bind to the -NH- links
    - the salt group dissociates when you dissolve the dye in water to give -SO3- groups.
    - to make -+NH2 groups need to add acid to provide H+ ions to -NH- groups.
    - the -SO3- groups then bind to the -+NH2- links
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what fibres do dyes have ionic interactions with?

A

wool, silk, nylon

they have -NH- links

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

are dyes that have ionic interactions with fibre colourfast

A

yes

better then hydrogen bonding dyes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do dyes attach themselves to fibres: covalent bonds

A

these are fibre reactive dyes
- most permanent

have a functional group that will react with the -OH or -NH- group in the fibre and form strong covalent bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are chromophores?

A

the structures in the molecules that give them their colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do chromophores give colour?

A

when light hits a chromophore, certain wavelengths are absorbed by electrons in the chromophore.

visible wavelengths not absorbed will be seen as a particular colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

structure of chromophores

A

tend to contain double or triple bonds, lone pairs of electrons, or benzene rings

these components usually form part of a delocalised system across a large section of the molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens when you modify a chromophore?

A

will change the frequency of light that it absorbs and so changes the colour of the molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How can you modify a chromophore?

A

functional groups containing O or N atoms with a lone pair of electrons can be added to a chromophore to adjust the colour of a dye molecule

because the lone pair of electrons become part of the delocalised system responsible for absorbing light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why do dyes need to be water soluble?

A

the process of dyeing usually involves soaking materials in a solution of the dye compound

ideally dissolves in water as water is cheap, readily available and non-toxic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how do you make dyes more soluble in water?

A

solubilising functional groups can be incorporated into a dye molecule

often ionic groups (such as the sulfate ions usually in the form of its sodium salt)
- water dissolves ionic substances because of its polar nature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly