Chapter 26 - Carboxylic Acids Flashcards
1
Q
what are CA made from?
A
primary alcohols
2
Q
what if there are 2 CA groups?
A
- dioic acid
e. g. propanedioic acid
3
Q
what can the carboxyl group be attached to?
A
a benzene ring e.g. benzenecarboxylic acid
4
Q
what is the name if an OH is attached to the CA?
A
add hydro- to first part of name e.g. hydrohexanoic acid
5
Q
which C IS C1 in a CA?
A
The COOH C
6
Q
Dissociation of Benzoic acid equation?
A
Benzoic acid (reversible ➡) Benzoate ion + H+
7
Q
benzoate ion not ?
A
BENZONOATE
8
Q
Why is a CA a weak acid?
A
only partially dissociates/ ionises into weak H+ ions in water
9
Q
How do CAs react ?
A
like normal acids
10
Q
Acid + metal ➡
A
H2 + metal salt
11
Q
Acid + metal Hydroxide ➡
A
H20 + salt
12
Q
Acid + carbonate ➡
A
CO2 + H2O + SALT
13
Q
Acid + metal Oxide ➡
A
H2O + salt
14
Q
ethanoic acid dissociation equation?
A
CH3COOH ➡(Reversible) CH3COO- + H+
15
Q
⭐ Remember?
A
reversible arrow as CAs are weak acids
16
Q
be careful w ?
A
charge on the metal ion
17
Q
how can esters be made?
A
by reacting a CA w an alcohol. This rac
18
Q
what is the ester FG?
A
-COO and it’s in the middle of the molecule
19
Q
which part of the ester comes from the alcohol?
A
-O-
20
Q
which part of the ester comes from the CA?
A
-C=O-
21
Q
what is an ester and what does this mean?
A
A derivative of a CA - this means that an ester can be hydrolysed (broken down by the addition of H2O) to form a CA
22
Q
How is an ester named?
A
- after CA
-oic acid is replaced with -oate
first part of name is from alcohol
23
Q
Reagents and Conditions needed to make an Ester?
A
R: An alcohol
C: Reflux w H2SO4
24
Q
ester prep: why is a water bath used?
A
for safety as ethanol and the ester are flammable
25
ester prep: why are anti-bumping granules added into the reflux flask?
to promote smooth boiling
26
ester prep: what is the role of conc H2S04?
- catalyst + dehydrating agent
| as it removes the water, the equilibrium shifts forwards forming more ester
27
ester prep: the esterification reaction is?
reversible so after reflux there is a mixture pf r+ p in the flask
28
ester prep: How is the sulfuric acid removed from the products?
- add 10cm3 of aq Na2CO3 at a time until no further fizzing, this neutralises acid forming a salt that is Na2CO3
29
ester prep: How is the sulfuric acid removed from the products?
- add 10cm3 of aq Na2CO3 at a time until no further fizzing, this neutralises acid forming a salt that is Na2SO4
- Na2CO3 + H2SO4 ➡ Na2SO + H2O + CO2
30
ester prep: why are there 2 layers in the separating funnel?
organic esters are insoluble in the water and H2SO4 is aq. The ester is less dense so floats on the surface of the aq layer.
31
ester prep: when the ester is removed from the separating funnel, why is some anhydrous sodium sulphate added?
a small amount of H2O is always left mixed w the ester, to dry ester
32
ester prep: what is the last stage?
redistill the ester to remove any remaining impurities
33
Uses of esters: Ethyl 2-methylbutanoate?
apple
34
Uses of esters: butyl butanoate?
pineapple
35
Uses of esters: 1-methylbutyl ethanoate?
banana
36
(general uses of esters)?
- solvents for chemical industry
- solvent for adhesives
- flower & plant fragrances used to make perfumes
- for flavouring food
37
what is hydrolyiss?
the chemical break down of a substance by reaction of water
38
conidtions for acid hydrolyiss of an ester?
reflux the ester w dilute HCl (aq) or dilute H2SO4
39
equation for acid hydrolysis of ester?
Ester + water ➡ CA+ alcohol (this is the reverse of esterification)
40
conditions for acid hydrolysis of an ester?
reflux the ester w dilute HCl (aq) or dilute H2SO4
41
equation for acid hydrolysis of ester?
Ester + water (acid not written in equation) ➡ CA+ alcohol (this is the reverse of esterification)
42
acid vs alkali hydrolysis of esters?
- acid produces CA+ alc but alkali produces carboxylate salt + alc
- acid involves reaction of ester w acid, but alkali w alkali
43
equation for alkali hydrolysis of ester?
ester + aq alkali ➡ alcohol + carboxylate salt
44
solubility of CAs?
- C=O and O-H bonds in CAs are polar, allowing them to form H bonds w H2O
- CAs with up to 4 C atoms are soluble in H2O
- As the number of C atoms ⬆, the solubility ⬇ as the non polar C chain has a greater effect on the overall polarity of the molecule
45
Dicarboxylic acids?
have 2 polar carboxyl grs to form H bonds. they are solids at room temp and dissolve readily in water
46
CAs take place in ? reactions
- redox (w metals) and neutralisations reactions (w bases - alkalis, metal oxides, carbonates)
47
how are carboxylate ions named?
by changing the -ic ending of the CA to -ate
48
CA derivatives have a ?
common sequence of atoms in their structure known as an acyl group - R-C=O. Esters, Acyl chlorides, acid anhydrides are all derivatives of CAs.
49
TO carry out acid hydrolysis?
- the ester is heated under reflux with dilute aq acid
| - the ester is broken down by water, w the acid acting as a catalyst
50
alkaline hydrolysis?
- known as saponification + is irreversible
| - ester heated under reflux w aq hydroxide ions
51
test for the carboxyl group?
- the neutralisation reaction of CAs w carbonates
- CAs are the only common organic compounds sufficiently acidic to react w carbonates.
- this is espec useful for distinguishing CAs from phenols - which aren't acidic enough to react w carbonates.
52
how to name CA?
- anoic ending
- no of Cs is the first part of the name - LONGEST CHAIN
- C in COOH is C1
53
Solubility of CAs?
decreases as chain length increases - as the chain length increases so does the number of induced dipole forces -> harder to break in order to dissolve -> molecule stays bonded together instead of dissolving
54
carboxylic acid salts have the ending?
-oate
55
reaction of a carboxylic acid + metal?
e.g.(ethan)oate + H2
56
reaction of a carboxylic acid + oxide?
-oate salt and water
57
reaction of a carboxylic acid + carbonate?
-oate and water
58
reaction of CA with alkali?
metal (ethan)oate
59
When writing the equation for an alcohol and CA?
Write the alcohol first and CA back to front as alcohol forms the first part of the name.
60
how to know which side of ester is from CA?
the side that contains the carbonyl bond is from the CA
61
uses of esters?
- solvents
- fragrances
- flavourings
62
⭐
look out for branches esters - if there's a branch on C1 of the alcohol then it's made from a secondary or tertiary alcohol
63
propan-2-ol becomes ? in an ester?
1-ethylmethyl
64
Alcohol name may be different ?
in the esters name!
65
Carboxylic acid loses?
the OH
66
Alcohol loses?
H
67
cyclocarboxylic acid?
a separate C with the OOH needs to be attached to the cyclo compound
68
when figuring out the name of the CA and Alc from the ester?
- break the O and the CO (ester bond)
| the O side is the alc side and the C=O side is the CA side
69
acid anhydrides FG?
c=o - o - c=o
70
how are anhydrides made?
from 2 CAs by removing a mol of water - one CA used loses OH and other loses H
71
how to name an anhydride?
look at one side of the O and count the number of carbons on that side (e.g. propanoic anydride has 6 Cs in total :)
72
anhydrides vs CAs?
anhydrides are CA derivatives but are MORE REACTIVE than CAs. They can also form esters.
73
making an ester using alc + CA vs making an ester from alc and acid anhydride?
- alc+ CA: reversible reaction, conc H2SO4 catalyst, reflux
| - alc + anhydride: non reversible, no catalyst needed, can be refluxed
74
2 reasons why chemists prefer to use anhydrides to prepare esters?
- anhydrides: irreverible reaction thfr ⬆ yield as reaction goes to completion
- anhydrides: CA is produced which can be sold so increased atom economy, water produced when CA is used
75
what happens when a dioic acid reacts w a base?
2 mol of base needed as 2 mol of H are lost from the dioic acid
76
what happens when a dioic acid reacts w a G2 metal?
the metal has a 2+ charge and the acid loses 2 H so no need to double the acid ion
- H is also produced
77
which C is C1?
first C of COOH
78
Solubility of CAs?
⬇as chain length ⬆
| more induced dipole forces, harder to overcome in order to dissolve
79
reaction of CA w metal?
2 CH3COOH + Mg ➡ (CH3COO-)2Mg2+ + H2
| magnesium ethanoate
80
reaction of CA w carbonate?
2CH3COOH + CaCO3 ➡ (CH3COO-)2Ca+ + H2O
| calcium ethanoate
81
reaction of CA w oxide?
2CH3COOH + CuO ➡ (CH3COO-)2Cu+ + H2O
| copper ethanoate
82
reaction of CA w alkali?
CH3COOH + NaOH ➡ CH3COONa + H2O
| sodium ethanoate
83
esterification REMEBER?
- water formed
- reversible arrow
- CA loses OH, Alc loses H
84
ester uses?
solvents
fragrances
flavourings
85
⭐ look out for?
Branched esters - if there's a branch on C1 of the alcohol, then its made from a 2/3' alc
86
acid hydrolysis is?
reversible
| alkali catalysed hydrolysis is not
87
alkali hydrolysis is the higher ? reaction
yield
88
NaOH splits into (alkali hydrolysis)
NaO and H
| H bonds to O and NaO to O of O=C
89
Propan-2-ol is what in an ester?
1-methylethyl
90
⭐
alcohol name may be diff in the ester name
91
how to work out the alc + CA from an ester?
- Break ester bond
- c=o is CA side
- o is alc side
92
anyhydrides?
- made from 2 CA molecules
- by removing a molecule of water (OH from 1, H from another)
- anhydrides have 2x as many Cs as the CA making em
93
why is it necessary to use an anhydride when forming an ester from phenol?
- they're both acids
- phenol is the weaker acid so it acts as a base (accepts protons)
- the anhydride is more acidic so it donates protons
- 2 ions formed
(reversible reaction)
94
CA derivatives?
have a common sequence of atoms in their structure known as acyl groups (RC=O)
All acyl groups are attached to a electronegative atom/ group of atoms
95
reactions of anhydrides?
- react w phenol to produce phenyl ???-oate and CA
| - react w water to form 2 CA molecules9
96
ACYL CHLORIDES?
- more reactive than anhydrides which are more reactive than CA
- used in OS
- high yield reactions
97
how are acyl chlorides prepared?
- reacting CA w thionyl chloride SOCl2
- reaction produces 3 products: HCl (g), SO2(g) both are acidic and corrosive
and the acyl chloride
98
acyl chlorides and acid anhydrides react INSTEAD OF?
CA
99
Reactions of acyl chlorides: w alc to form ester?
HCl ALWAYS FORMED, rest of mols just join up lol
100
when acyl chlorides form esters?
arrow is NOT reversible
101
when acyl chlorides react w phenol?
- ester formed - phenyl ???-oate, HCl formed
| - join whats left together
102
for it to be safer when making an ester?
use acid anhydride not acyl chlorides as HCl formed when acyl chlorides used
103
other reactions of acyl chlorides?
- react w water
- it's a very vigorous reaction
HCl formed + CA
104
what is the advantage of using CA derivatives?
using anhydrides and acyl chlorides in reactions like esterification means no catalyst required
