A base, in chemistry, refers to any substance that releases hydroxide ions (OH−) when dissolved in water or an aqueous solution.
Many bases, however, don’t readily carry hydroxide ions, but they, too, produce high levels of OH− when treated with water. This type of reaction can be observed when ammonia is treated with water to produce ammonium and hydroxide.
Bases also have distinctive physical characteristics; for example, they are bitter in taste (acids are sour) and give a slippery sensation when touched.
Bases are essential and are a vital ingredient in specific industries. They are used to make paper, soap, synthetic rayon, bleaching powder, antacids, etc. While they are generally considered the chemical opposite of acids, there are few known acids that can behave just like bases under certain circumstances.
Just like acids, bases can also be either strong or weak. A strong base is simply a chemical compound that breaks apart (dissociates) completely into water and yields hydroxide ions.
Common examples of strong bases are NaOH (Sodium hydroxide) and Ca(OH)2 (Calcium hydroxide). Whereas, a weak base dissociates into the water only to a certain degree.
What is superbase?
Superbase(s) are potent chemical compounds that have an extremely high affinity for protons and are stronger than hydrogen ions. They play a crucial role in organic synthesis and are essential in physical organic chemistry.
The term “superbase” has been around for over a century and a half. Because superbases can react violently when they touch water or carbon dioxide, they need a special solvent for chemical reactions. Superbases fall into three categories: organic, inorganic, and organometallic.
Below, we have featured some of the strongest bases ever synthesized worldwide. Most of them are classified as either inorganic or organometallic compounds.
Table of Contents
12. Sodium Hydroxide
A working model of the Chloralkali process or Chloralkali electrolysis
Chemical Formula: NaOH
Sodium hydroxide, popularly known as caustic soda, is an ionic compound that carries sodium cations Na+ and hydroxide anions OH–. NaOH is known for its extremely corrosive nature, especially at room temperature, as it can quickly decompose proteins. It is capable of attracting (absorbing) CO2 and moisture from the air.
Sodium hydroxide is largely used for chemical pulping in the paper industry. Its other applications include soaps and detergent manufacturing, raw food processing, cement manufacturing, and water treatment facilities to neutralize the pH values of water. It is also used in the petroleum industry from time to time to neutralize acids and increase the alkalinity levels of a certain solution.
In ancient times, NaOH was produced by treating calcium hydroxide with sodium carbonate. By the 19th century, it was replaced by the Solvay process, which was used to produce sodium carbonate, a cheap alternative to NaOH. Today, most of the industrial sodium hydroxide is created through the chloralkali process.
11. Potassium tert-butoxide
Ball-and-stick model of C4H9KO (Potassium is in purple, and Oxygen is in red)
Chemical Formula: C4H9KO
Potassium tert-butoxide, abbreviated as KOtBu, is a strong base and a popular reagent in organic synthesis.
While it is found as a white to off-white crystalline solid, it can be prepared by reacting tert-butyl alcohol with potassium metal in a suitable solvent such as tetrahydrofuran or diethyl ether.
Potassium tert-butoxide is used in deprotonation reactions, especially in the synthesis of organometallic compounds, enolates, and alkoxides.
It is also used to prepare various pharmaceuticals, agrochemicals, and specialty chemicals due to its versatility and efficiency as a reagent. As per reports, Potassium tert-butoxide’s market size will exceed $25.6 billion by 2027, growing at a CAGR of 6.5%.
10. Lithium Hydroxide
This is huge – 350MW geothermal plant plus 175K annual tons of Lithium Hydroxide production (2022 global production = 180K tons)https://t.co/e7fW5WFj8C
— John Smillie (@JohnSmillie42) January 25, 2024
Chemical Formula: LiOH
Lithium hydroxide is a white crystalline substance in its anhydrous form. It dissolves readily in water and has a corrosive nature. It’s known as the least strong among all alkali metal hydroxides.
Lithium hydroxide is produced by inducing a reaction between calcium hydroxide and lithium carbonate in a salt metathesis reaction.
Li2CO3 + Ca(OH)2 → 2 LiOH + CaCO3
A large amount of LiOH is used to manufacture lithium soaps. Additionally, lithium hydroxide is used in the ventilation systems of submarines and spacecraft to eliminate carbon dioxide by generating water and lithium carbonate.
2 LiOH + CO2 → Li2CO3 + H2O
It is also used as a corrosion control measure in nuclear reactors (pressurized water reactors) and as a battery electrolyte.
9. Potassium Hydroxide
Chemical Formula: KOH
Many of you may recognize potassium hydroxide as a caustic potash, which is a solid white substance known for its highly corrosive nature. Like sodium hydroxide, KOH is colorless (though commercially available in white) and is a strong quintessential base.
While potassium hydroxide and sodium hydroxide can be used interchangeably for various purposes, most industries use NaOH since it’s the cheaper of the two. Anyway, it is used to produce bio-diesel, manufacture soaps, and as an electrolyte in some batteries.
Pure potassium hydroxide is produced by reacting sodium hydroxide with degraded or impure potassium. The chemical compound is potentially hazardous and causes skin burns when the concentration is more than 2%. Anything between 0.5% to 2% can cause severe irritations.
8. Lithium bis(trimethylsilyl)amide
Chemical Formula: C6H18LiNSi2
Lithium bis(trimethylsilyl)amide, or LiHMDS, is a non-nucleophilic superbase that has several crucial applications in laboratories.
Similar to other lithium-based reagents, it has the ability to create cyclic compounds by forming trimers, which are anions consisting of three ions of the same substance.
LiHMDS is usually prepared by reacting bis(trimethylsilyl)amine with Butyllithium.
HN(SiMe3)2 + C4H9Li → LiN(SiMe3)2 + C4H10
7. Sodium Hydride
Chemical Formula: NaH
Sodium hydride belongs to a special group of hydrides known as saline/ionic hydrides (composed of Na+ and H− ions), which exist in salt-like form, unlike ammonia and water.
It’s largely used as a base in organic synthesis, though a few insignificant uses of NaH are also known. Sodium hydride is produced by reacting hydrogen with liquid sodium.
Pure sodium hydride is colorless, but commercial samples can appear grey. Furthermore, NaH is about 40% denser than its precursor chemical compound, sodium.
In rare cases, the compound can take the form of ‘inverse sodium hydride’, where sodium and hydrogen ion swap charges (Na− and H+). Na− is an alkalide, which makes this compound more energetic than the standard sodium hydroxide (due to the increased net displacement between the two electrons).
NaH is pyrophoric in nature. It also reacts violently with water and produces sodium hydroxide, a corrosive substance, when it goes through hydrolysis.
6. Potassium Amide
Chemical Formula: KNH2
Potassium Amide is a strong base and a powerful nucleophile. It exists as a white crystalline solid with a crystal lattice structure. This structure plays a vital role in its reactivity and stability.
It is commonly prepared by reacting gaseous ammonia with potassium metal in a non-polar solvent like liquid ammonia.
In laboratory settings, potassium amide serves as a versatile reagent for organic synthesis and other chemical transformations. For example, it facilitates processes such as deprotonation of acidic hydrogens, elimination reactions, and formation of metal-organic complexes.
Various studies have been conducted to explore the potential of potassium amide in hydrogen storage systems. It can react reversibly with hydrogen gas, which makes it a suitable candidate for storing and releasing hydrogen in fuel cell applications.
5. Sodium Amide
Chemical Formula: NaNH2
Sodium azide, sometimes known as sodium amide, is one of the strongest known bases in the world. It’s an important, commercially available chemical compound that is generally used in organic synthesis.
NaNH2 conducts electricity (in a fused state) since its electrical conductance properties are almost similar to that of sodium hydroxide.
While pure sodium hydroxide is usually white, most of the commercially available NaNH2 is grey in color due to the presence of impurities in the form of metallic iron. Typically, sodium amide is prepared by reacting ammonia gas with sodium.
2 Na + 2 NH3 → 2 NaNH2 + H2
Sodium amide is preferred in certain types of synthesis due to its functions as a nucleophile. It’s a potentially dangerous chemical substance, which must be handled with extreme caution. It can react vigorously with water, especially when present in solid form
4. Lithium diisopropylamide
Use of Lithium Diisopropylamide in Flow: Operability and Safety Challenges Encountered on a Multigram Scale https://t.co/cOgRGLk7XB
— Scientific Update (@SciUp) March 31, 2021
Chemical Formula: C6H14LiN
Next on the list is Lithium diisopropylamide, another non-nucleophilic superbase that is known for its highly corrosive nature and solubility. Under normal conditions, the compound is synthesized by treating a cooled diisopropylamine solution (tetrahydrofuran) with Butyllithium.
Needless to say, lithium diisopropylamide is corrosive and pyrophoric, but commercial solutions are much safer.
Image Courtesy: Rockwood Lithium
Chemical Formula: C4H9Li
n-Butyllithium or n-BuLi, for short, is a commercially important superbase, mostly used as a catalyst for polymerization to produce synthetic rubber. It has uses in the pharmaceutical industry as well.
Although Butyllithium is primarily colorless, it can go through mild color changes either when it comes in contact with alkanes or when it ages.
Apart from being a superbase, n-BuLi is a powerful reducing agent as well as a nucleophile (a chemical that donates an electron pair to form a bond). Butyllithium is generally produced by reacting lithium with either 1-bromobutane or 1-chlorobutane.
2 Li + C4H9X → C4H9Li + LiX
Butyllithium is unstable and can react vigorously with water and carbon dioxide, but it can be stored safely under inert gas.
2. Lithium monoxide anion
Chemical Formula: LiO−
Epa: 1782 kJ/mol−1
Lithium monoxide anion was once the world’s strongest base before it was dethroned in 2008. Like other superbases, lithium monoxide is prepared in an aprotic solvent and is also known for its extremely corrosive nature.
The synthesis of lithium monoxide anion is a complicated procedure and is challenging to carry out in a controlled manner. Usually, a small amount of lithium oxalate (Li2C2O4) is used as the precursor, which goes through the electrospray ionization process. The resulting compound lithium oxalate anion (LiC2O4) is isolated and then processed with collision-induced dissociation twice.
As a result, we get a Lithium monoxide anion (LiO−) and a Carbon dioxide molecule. There is no known use of lithium monoxide anion.
1. ortho-Diethynylbenzene dianion
Preparation of o-diethynylbezene dianion
Chemical Formula: [C6H4(C2)2]2−
Epa: 1843 kJ/mol
ortho-Diethynylbenzene dianion is perhaps the strongest base known to us. It was initially synthesized/discovered by a group of researchers in Australia using mass spectrometry.
Like other superbases, ortho-diethynylbenzene dianion can only be kept in the gaseous phase. This, however, provides an ideal environment to measure its basicity levels with greater precision.
Calculations have shown that ortho-diethynylbenzene dianion has a proton affinity of 1843 kJ/ mol−1, far more than that of hydroxide (1,633.14 kJ/mol).
Furthermore, ortho-diethynylbenzene dianion has two isomers (with the same molecular formula but different chemical structures): Meta-diethynylbenzene dianion and Para-diethynylbenzene dianion, the second and third strongest base ever synthesized.
Both the isomers, including ortho-Diethynylbenzene dianion, have no known use and exist in the gaseous state.
Frequently Asked Questions
What are weak bases?
Weak bases do not completely dissociate into their constituent ions when dissolved in water or an aqueous solution. Some parts of the weak base break apart into ions while others parts remain undissociated inside the solution.
As compared to strong bases that dissociate 100% in solution, weak bases dissociate only 5-10%.
Ammonia, ferric hydroxide, zinc hydroxide, aluminum hydroxide, copper hydroxide, and methylamine are among the most common examples of weak bases.
In fact, you encounter weak bases in your everyday life. Baking soda used in baking cakes, antacids in your medicine cabinet, and household cleaners containing ammonia—all fall under the category of weak bases.
How are bases different from alkalis?
Bases that dissolve in water are alkalis. It is important to note that all alkalies are base, but the reverse is not true.
The term “alkali” is often used more narrowly to refer to bases that dissolve in water to form alkaline solutions, whereas “base” is a broader term that includes substances with a range of chemical properties.
Bases that neutralize acids are metal hydroxides and metal oxides. Alkalis are also metal oxides, but they can dissolve in water, releasing hydroxide ions. For example, Copper oxide and Zinc hydroxide are bases, while ammonia and magnesium hydroxide are alkalis.
Although alkalis are usually soluble in water, some exceptions do exist. Barium carbonate, for instance, is only soluble when it reacts with an acidic aqueous solution.
What base is used in toothpaste?
Toothpaste contains mild bases such as sodium carbonate, sodium fluoride, and magnesium hydroxide. They react with acids (produced by bacteria and germs) in our mouth and neutralize them to keep our teeth clean and healthy.