mathematics

Phosphonate

Phosphonate is a mathematics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Phosphonate rather than just read about it. In short: In organic chemistry, phosphonates or phosphonic acids are organophosphorus compounds containing C−PO(OR)2 groups, where R is an organic group (alkyl, aryl). If R is hydrogen then the compound is a dialkyl phosphite, which is a different functional group.

Key takeaways

Phosphonate belongs to mathematics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Phosphonate to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Phosphonate from memory before moving on to harder problems.

Reference excerpt

In organic chemistry, phosphonates or phosphonic acids are organophosphorus compounds containing C−PO(OR)2 groups, where R is an organic group (alkyl, aryl). If R is hydrogen then the compound is a dialkyl phosphite, which is a different functional group. Phosphonic acids, typically handled as salts, are generally nonvolatile solids that are poorly soluble in organic solvents, but soluble in water and common alcohols. Many commercially important compounds are phosphonates, including glyphosate (the active molecule of the herbicide Roundup), and ethephon, a widely used plant growth regulator. Bisphosphonates are popular drugs for treatment of osteoporosis.

In biochemistry and medicinal chemistry, phosphonate groups are used as stable bioisosteres for phosphate, such as in the antiviral nucleotide analog, Tenofovir, one of the cornerstones of anti-HIV therapy. And there is an indication that phosphonate derivatives are "promising ligands for nuclear medicine."

Basic properties Phosphonates feature tetrahedral phosphorus centers. They are structurally closely related to (and often prepared from) phosphorous acid.

Phosphonate salts are the result of deprotonation of phosphonic acids, which are diprotic acids:

RPO(OH)2 + NaOH → H2O + RPO(OH)(ONa) (monosodium phosphonate) RPO(OH)(ONa) + NaOH → H2O + RPO(ONa)2 (disodium phosphonate) Phosphonate esters are the result of condensation of phosphonic acids with alcohols.

Synthesis Several methods exist for the preparation of phosphonic acids and their salts.

From phosphonic acid Most processes begin with phosphorous acid (aka phosphonic acid, H3PO3), exploiting its reactive P−H bond. Phosphonic acid can be alkylated via the Kabachnik–Fields reaction or Pudovik reaction to give aminophosphonate, which are useful as chelating agents. One example is the industrial preparation of nitrilotris(methylenephosphonic acid):

NH3 + 3 H3PO3 + 3 CH2O → N(CH2PO3H2)3 + 3 H2O Phosphonic acid also can be alkylated with acrylic acid derivatives to afford carboxyl functionalized phosphonic acids. This reaction is a variant of the Michael addition:

CH2=CHCO2R + 3 H3PO3 → (HO)2P(O)CH2CH2CO2R In the Hirao coupling dialkyl phosphites (which can also be viewed as di-esters of phosphonic acid: (O=PH(OR)2) undergo a palladium-catalyzed coupling reaction with an aryl halide to form a phosphonate.

Michaelis-Arbuzov reaction Phosphonic esters are prepared using the Michaelis–Arbuzov reaction. For example, methyl iodide catalyses the conversion of trimethylphosphite to the phosphonate ester dimethyl methylphosphonate:

P(OMe)3 → MePO(OMe)2 These esters can be hydrolysed to the acid (Me = methyl):

MePO(OMe)2 + H2O → MePO(OH)2 + 2 MeOH In the Michaelis–Becker reaction, a hydrogen phosphonate diester is first deprotonated and the resulting anion is alkylated.

From phosphorus trichloride Vinylphosphonic acid can be prepared by the reaction of PCl3 and acetaldehyde:

PCl3 + CH3CHO → CH3CH(O−)PCl+3 This adduct reacts with acetic acid:

CH3CH(O−)PCl+3 + 2 CH3CO2H → CH3CH(Cl)PO(OH)2 + 2 CH3COCl This chloride undergoes dehydrochlorination to afford the target:

CH3CH(Cl)PO(OH)2 → CH2=CHPO(OH)2 + HCl In the Kinnear–Perren reaction alkylphosphonyl dichlorides and esters are generated by alkylation of phosphorus trichloride in the presence of aluminium trichloride. Alkyltrichlorophosphonium salts are intermediates:

PCl3 + RCl + AlCl3 → RPCl+3 + AlCl−4 The RPCl+3 product can then be decomposed with water to produce an alkylphosphonic dichloride RP(=O)Cl2.

Reactions

Hydrolysis Phosphonate esters are generally susceptible to hydrolysis under both acidic and basic conditions. Cleavage of the P-C bond is harder but can be achieved under aggressive conditions.

O=PC(OR)2 + 2 H2O → O=PC(OH)2 + 2 ROH

Horner–Wadsworth–Emmons reaction In the Horner–Wadsworth–Emmons reaction dialkyl-phosphonates are deprotonated to give stabilized carbanions, which react with aldehydes to give E-alkenes with elimination of a dialkyl-phosphate.

Structural sub-classes

Bisphosphonates

Compounds containing 2 geminal phosphonate groups are known as bisphosphonates. They were first synthesized in 1897 by Von Baeyer and Hofmann and now form the basis for an important class of drugs, used to treat osteoporosis and similar diseases. Examples include HEDP (etidronic acid or Didronel), which is prepared from phosphorous acid and acetic anhydride:

2 H3PO3 + (CH3CO)2O → CH3C(OH)(PO3H2)2 + CH3CO2H

Thiophosphonates

A thiophosphonate group is a functional group related to phosphonate by substitution of an oxygen atom for a sulphur. They are a reactive component of many pesticides and nerve agents. Substituted thiophosphonates can have two main structural isomers bonding though either O or S groups to give thione and thiol forms respectively. This is a property they share with related functional groups such as thiocarboxylic acids and organothiophosphates.

Phosphonamidates

Phosphonamidates are related to phosphonates by substitution of an oxygen atom for a nitrogen. They are a rarely encountered functional group. The nerve agent Tabun is an example.

Occurrence in nature

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Phosphonate

Start with the simplest possible case. Write down what Phosphonate claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In mathematics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Phosphonate before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Phosphonate ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Phosphonate

In research: Phosphonate appears in mathematics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Phosphonate in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Phosphonate is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chelating agents, Concrete admixtures, Functional groups, so understanding it makes those chapters shorter.
In everyday life: Look for Phosphonate outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Phosphonate in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Phosphonate means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Phosphonate out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Phosphonate in simple terms?

Why does Phosphonate matter?

Because it connects several mathematics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Phosphonate?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Phosphonate.