Nomenclature of carboxylic acids and their salts

The IUPAC name of a carboxylic acid is derived from that of the longest carbon chain that contains the carboxyl group by dropping the final -e from the name of the parent alkane and adding the suffix -oic followed by the word “acid.” The chain is numbered beginning with the carbon of the carboxyl group. Because the carboxyl carbon is understood to be carbon 1, there is no need to give it a number. For example, the compound CH₃CH₂COOH has three carbon atoms and is called propanoic acid, from propane, the name for a three-carbon chain, with -oic acid, the suffix for this class of compounds, appended. If the carboxylic acid contains a carbon-carbon double bond, the ending is changed from -anoic acid to -enoic acid to indicate the presence of the double bond, and a number is used to show the location of the double bond.

Most simple carboxylic acids, rather than being called by their IUPAC names, are more often referred to by common names that are older than their systematic names. Most simple carboxylic acids were originally isolated from biological sources; because their structural formulas were often unknown at the time of isolation they were given names that were generally derived from the names of the sources. For example, CH₃CH₂CH₂COOH, butyric acid, first obtained from butter, was named after the Latin butyrum, meaning “butter.” The acids containing an odd number of carbon atoms greater than nine generally do not have common names. The reason is that long-chain carboxylic acids were originally isolated from fats (which are carboxylic esters), and generally these fats contain carboxylic acids with only an even number of carbon atoms (because the process by which living organisms synthesize such fatty acids puts the molecules together in two-carbon pieces).

When common names are used, substituents on the hydrocarbon chain are designated by Greek letters rather than by numbers, and counting begins not with the carboxyl carbon but with the adjacent carbon. For example, the common name of the following compound γ-aminobutyric acid, abbreviated GABA. Its IUPAC name is 4-aminobutanoic acid. GABA is an inhibitory neurotransmitter in the central nervous system of humans.

Salts of carboxylic acids are named in the same manner as are the salts of inorganic compounds; the cation is named first and then the anion, as in sodium chloride. For carboxylic acids, the name of the anion is derived by changing the ending -oic acid of the IUPAC name or -ic acid of the common name to -ate. Some examples are sodium acetate, CH₃COONa; ammonium formate, HCOONH₄; and potassium butanoate (potassium butyrate), CH₃CH₂CH₂COOK.

Properties of carboxylic acids

Acidity

The most important property of carboxylic acids, and the one that is responsible for naming them such, is their acidity. An acid is any compound that donates a hydrogen ion, H⁺ (also called a proton), to another compound, termed a base Carboxylic acids do this much more readily than most other classes of organic compounds, so they are said to be stronger acids, even though they are much weaker than the most important mineral acids—sulfuric (H₂SO₄), nitric (HNO₃), and hydrochloric (HCl). The reason for the enhanced acidity of this group of compounds can best be demonstrated by a comparison of their acidity with that of alcohols, both of which contain an ―OH group. Alcohols are neutral compounds in aqueous solution. When an alcohol donates its proton, it becomes a negative ion called an alkoxide ion, RO⁻. When a carboxylic acid donates its proton, it becomes a negatively charged ion, RCOO⁻, called a carboxylate ion.

A carboxylate ion is much more stable than the corresponding alkoxide ion because of the existence of resonance structures for the carboxylate ion which disperse its negative charge. Only one structure can be drawn for an alkoxide ion, but two structures can be drawn for a carboxylate ion. When two or more structures that differ only in the positions of valence electrons can be drawn for a molecule or ion, it means that its valence electrons are delocalized, or spread over more than two atoms. This phenomenon is called resonance, and the structures are called resonance forms. A double-headed arrow is used to show that the two or more structures are related by resonance. Because there are two resonance forms but only one real ion, it follows that neither of these forms is an accurate representation of the actual ion. The real structure incorporates aspects of both resonance structures but duplicates neither. Resonance always stabilizes a molecule or ion, even if charge is not involved. The stability of an anion determines the strength of its parent acid. A carboxylic acid is, therefore, a much stronger acid than the corresponding alcohol, because, when it loses its proton, a more stable ion results.

Some atoms or groups, when attached to a carbon, are electron-withdrawing, as compared with a hydrogen atom in the same position. For example, consider chloroacetic acid (Cl―CH₂COOH) compared with acetic acid (H―CH₂COOH). Because chlorine has a higher electronegativity than hydrogen, the electrons in the Cl―C bond are drawn farther from the carbon than the electrons in the corresponding H―C bond. Thus, chlorine is considered to be an electron-withdrawing group. This is one example of the so-called inductive effect, in which a substituent affects a compound’s distribution of electrons. There are a number of such effects, and atoms or groups may be electron-withdrawing or electron-donating as compared with hydrogen. The presence of such groups near the COOH group of a carboxylic acid often has an effect on the acidity. In general, electron-withdrawing groups increase acidity by increasing the stability of the carboxylate ion. In contrast, electron-donating groups decrease acidity by destabilizing the carboxylate ion. For example, the methyl group, ―CH₃, is generally regarded as electron-donating, and acetic acid, CH₃ COOH, is about 10 times weaker as an acid than formic acid, HCOOH. Similarly, chloroacetic acid, ClCH₂ COOH, in which the strongly electron-withdrawing chlorine replaces a hydrogen atom, is about 100 times stronger as an acid than acetic acid, and nitroacetic acid, NO₂CH₂ COOH, is even stronger. (The NO₂ group is a very strong electron-withdrawing group.) An even greater effect is found in trichloroacetic acid, Cl₃CCOOH, whose acid strength is about the same as that of hydrochloric acid.

Solubility

The solubility of carboxylic acids in water is similar to that of alcohols, aldehydes, and ketones. Acids with fewer than about five carbons dissolve in water; those with a higher molecular weight are insoluble owing to the larger hydrocarbon portion, which is hydrophobic. The sodium, ammonium, and potassium salts of carboxylic acids, however, are generally quite soluble in water. Thus, almost any carboxylic acid can be made to dissolve in water by converting it to such a salt, which is easily done by adding a strong base—most commonly sodium hydroxide (NaOH) or potassium hydroxide, (KOH). The calcium and sodium salts of propanoic (propionic) acid are used as preservatives, chiefly in cheese, bread, and other baked goods.

Pure acetic acid, often called glacial acetic acid, is a corrosive, colourless liquid (boiling point 117.9 °C [244.2 °F]; melting point 16.6 °C [61.9 °F]) that is completely miscible with water

Classification of the substance or mixture
Flammable liquids, (Category 3) H226: Flammable liquid and vapor.
Skin corrosion, (Sub-category
1A)
H314: Causes severe skin burns and eye
damage.
Serious eye damage, (Category
1)
H318: Causes serious eye damage.

Signal Word Danger
Hazard Statements
H226 Flammable liquid and vapor.
H314 Causes severe skin burns and eye damage.
Precautionary Statements
P210 Keep away from heat, hot surfaces, sparks, open flames and
other ignition sources. No smoking.
P233 Keep container tightly closed.
P240 Ground and bond container and receiving equipment.
P280 Wear protective gloves/ protective clothing/ eye protection/ face
protection.
P303 + P361 + P353 IF ON SKIN (or hair): Take off immediately all contaminated
clothing. Rinse skin with water.
P305 + P351 + P338 IF IN EYES: Rinse cautiously with water for several minutes.
Remove contact lenses, if present and easy to do. Continue
rinsing.
Supplemental Hazard
Statements
none.

Signal Word Danger
Hazard Statements
H314 Causes severe skin burns and eye damage.
Precautionary Statements
P280 Wear protective gloves/ protective clothing/ eye protection/ face
protection.
P303 + P361 + P353 IF ON SKIN (or hair): Take off immediately all contaminated
clothing. Rinse skin with water.
P305 + P351 + P338 IF IN EYES: Rinse cautiously with water for several minutes.
Remove contact lenses, if present and easy to do. Continue
rinsing.
Supplemental Hazard
Statements
none.

This substance/mixture contains no components considered to be either persistent,
bioaccumulative and toxic (PBT), or very persistent and very bioaccumulative (vPvB) at
levels of 0.1% or higher.

Ecological information:

Aldrich- W200603 Page 3 of 14
The life science business of Merck operates as MilliporeSigma in the US and
Canada
The substance/mixture does not contain components considered to have endocrine
disrupting properties according to REACH Article 57(f) or Commission Delegated regulation
(EU) 2017/2100 or Commission Regulation (EU) 2018/605 at levels of 0.1% or higher.
Toxicological information:
The substance/mixture does not contain components considered to have endocrine
disrupting properties according to REACH Article 57(f) or Commission Delegated regulation
(EU) 2017/2100 or Commission Regulation (EU) 2018/605 at levels of 0.1% or higher.
Lachrymator .

Substances
Synonyms : Glacial acetic acid
Formula : C2H4O2
Molecular weight : 60,05 g/mol
CAS-No. : 64-19-7
EC-No. : 200-580-7
Index-No. : 607-002-00-6
Component Classification Concentration
acetic acid
CAS-No.
EC-No.
Index-No.
64-19-7
200-580-7
607-002-00-6
Flam. Liq. 3; Skin Corr.
1A; Eye Dam. 1; H226,
H314, H318
Concentration limits:
>= 90 %: Skin Corr. 1A,
H314; 25 – < 90 %: Skin
Corr. 1B, H314; 10 – < 25
%: Skin Irrit. 2, H315; 10
– < 25 %: Eye Irrit. 2,
H319;
<= 100 %.

Description of first-aid measures
General advice
First aiders need to protect themselves. Show this material safety data sheet to the doctor
in attendance.
If inhaled
After inhalation: fresh air. Call in physician.
In case of skin contact
In case of skin contact: Take off immediately all contaminated clothing. Rinse skin with
water/ shower. Call a physician immediately.

In case of eye contact
After eye contact: rinse out with plenty of water. Immediately call in ophthalmologist.
Remove contact lenses.
If swallowed
After swallowing: make victim drink water (two glasses at most), avoid vomiting (risk of
perforation). Call a physician immediately. Do not attempt to neutralise.

uitable extinguishing media
Water Foam Carbon dioxide (CO2) Dry powder
Unsuitable extinguishing media
For this substance/mixture no limitations of extinguishing agents are given.

Special hazards arising from the substance or mixture
Carbon oxides
Combustible.
Vapors are heavier than air and may spread along floors.
Forms explosive mixtures with air at elevated temperatures.
Development of hazardous combustion gases or vapours possible in the event of fire.

Advice for firefighters
Stay in danger area only with self-contained breathing apparatus. Prevent skin contact by
keeping a safe distance or by wearing suitable protective clothing.

Further information
Remove container from danger zone and cool with water. Prevent fire extinguishing water
from contaminating surface water or the ground water system.

Personal precautions, protective equipment and emergency procedures
Advice for non-emergency personnel: Do not breathe vapors, aerosols. Avoid substance
contact. Ensure adequate ventilation. Keep away from heat and sources of ignition.
Evacuate the danger area, observe emergency procedures, consult an expert.
For personal protection see section 8.

Environmental precautions
Do not let product enter drains. Risk of explosion.

Methods and materials for containment and cleaning up
Cover drains. Collect, bind, and pump off spills. Observe possible material restrictions
(see sections 7 and 10). Take up with liquid-absorbent and neutralising material (e.g.
Chemizorb® H⁺, Merck Art. No. 101595). Dispose of properly. Clean up affected area.

Precautions for safe handling
Advice on protection against fire and explosion
Keep away from open flames, hot surfaces and sources of ignition.Take precautionary
measures against static discharge.
Hygiene measures
Immediately change contaminated clothing. Apply preventive skin protection. Wash hands
and face after working with substance.
For precautions see section 2.2.

Conditions for safe storage, including any incompatibilities
Storage conditions
Keep container tightly closed in a dry and well-ventilated place. Keep away from heat and
sources of ignition.
Storage class
Storage class (TRGS 510): 3: Flammable liquids

Specific end use(s)
Apart from the uses mentioned in section 1.2 no other specific uses are stipulated.

Application Area Routes of
exposure
Health effect Value
Workers Inhalation Acute local effects 25 mg/m3
Workers Inhalation Long-term local effects 25 mg/m3
Workers Skin contact Long-term local effects 10mg/kg BW/d
Consumers Inhalation Acute local effects 25 mg/m3
Consumers Inhalation Long-term local effects 25 mg/m3
Predicted No Effect Concentration (PNEC)
Compartment Value
Soil 0,478 mg/kg
Sea water 0,3058 mg/l
Fresh water 3,058 mg/l
Sea sediment 1,136 mg/kg
Fresh water sediment 11,36 mg/kg
Sewage treatment plant 85 mg/l
Aquatic intermittent release 30,58 mg/l.

Eye/face protection
Use equipment for eye protection tested and approved under appropriate
government standards such as NIOSH (US) or EN 166(EU). Tightly fitting safety
goggles
Skin protection
This recommendation applies only to the product stated in the safety data sheet,
supplied by us and for the designated use. When dissolving in or mixing with other
substances and under conditions deviating from those stated in EN 16523-1 please
contact the supplier of CE-approved gloves (e.g. KCL GmbH, D-36124 Eichenzell,
Internet: www.kcl.de).
Full contact
Material: butyl-rubber
Minimum layer thickness: 0,7 mm
Break through time: 480 min
Material tested:Butoject® (KCL 898)
This recommendation applies only to the product stated in the safety data sheet,
supplied by us and for the designated use. When dissolving in or mixing with other
substances and under conditions deviating from those stated in EN 16523-1 please
contact the supplier of CE-approved gloves (e.g. KCL GmbH, D-36124 Eichenzell,
Internet: www.kcl.de).
Splash contact
Material: Latex gloves
Minimum layer thickness: 0,6 mm
Break through time: 30 min
Material tested:Lapren® (KCL 706 / Aldrich Z677558, Size M)
Body Protection
Flame retardant antistatic protective clothing.
Respiratory protection
Recommended Filter type: filter E-(P2)
The entrepeneur has to ensure that maintenance, cleaning and testing of respiratory
protective devices are carried out according to the instructions of the producer.
These measures have to be properly documented.

a)Physical state liquid
b) Color colorless
c) Odor stinging
Aldrich- W200603 Page 7 of 14
The life science business of Merck operates as MilliporeSigma in the US and
Canada
d) Melting
point/freezing point
Melting point/range: 16,2 °C – lit.
e) Initial boiling point
and boiling range 117 – 118 °C
f) Flammability (solid,
gas)
No data available
g) Upper/lower
flammability or
explosive limits
Upper explosion limit: 19,9 %(V)
Lower explosion limit: 4 %(V)
h) Flash point 39 °C – closed cup
i) Autoignition
temperature
463 °C
j) Decomposition
temperature
Distillable in an undecomposed state at normal pressure.
k) pH 2,5 at 50 g/l at 20 °C
l) Viscosity Viscosity, kinematic: 1,17 mm2/s at 20 °C
Viscosity, dynamic: 1,05 mPa.s at 25 °C
m) Water solubility 602,9 g/l at 25 °C at 1.013 hPa – completely soluble
n) Partition coefficient:
n-octanol/water
log Pow: -0,17 at 25 °C – Bioaccumulation is not expected.,
(ECHA)
o) Vapor pressure 20,79 hPa at 25 °C
p) Density 1,049 g/cm3 at 25 °C – lit.
Relative density No data available
q) Relative vapor
density
No data available
r) Particle
characteristics
No data available
s) Explosive properties No data available
t) Oxidizing properties none