chemistry

Guanidinium chloride

Guanidinium chloride is a chemistry 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 Guanidinium chloride rather than just read about it. In short: Guanidinium chloride or guanidine hydrochloride, usually abbreviated GdmCl and sometimes GdnHCl or GuHCl, is the hydrochloride salt of guanidine. Structure Guanidinium chloride crystallizes in orthorhombic space group Pbca.

Key takeaways

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

Reference excerpt

Guanidinium chloride or guanidine hydrochloride, usually abbreviated GdmCl and sometimes GdnHCl or GuHCl, is the hydrochloride salt of guanidine.

Structure

Guanidinium chloride crystallizes in orthorhombic space group Pbca. The crystal structure consists of a network of guanidinium cations and chloride anions linked by N–H···Cl hydrogen bonds.

Acidity Guanidinium chloride is a weak acid with a pKa of 13.6. The reason that it is such a weak acid is the complete delocalization of the positive charge through three nitrogen atoms (plus a little bit of positive charge on carbon). However, some stronger bases can deprotonate it, such as sodium hydroxide:

C(NH2)+3 + OH− ⇌ HNC(NH2)2 + H2O The equilibrium is not complete because the acidity difference between guanidinium and water is not large. The approximate pKa values: 13.6 vs 15.7. Complete deprotonation should be done with extremely strong bases, such as lithium diisopropylamide.

C(NH2)+3Cl− + Li+N(C3H7)−2 → HNC(NH2)2 + HN(C3H7)2 + LiCl

Use in protein denaturation Guanidinium chloride is a strong chaotrope and one of the strongest denaturants used in physiochemical studies of protein folding. It also has the ability to decrease enzyme activity and increase the solubility of hydrophobic molecules. At high concentrations of guanidinium chloride (e.g., 6 M), proteins lose their ordered structure, and they tend to become randomly coiled, i.e. they do not contain any residual structure. However, at concentrations in the millimolar range in vivo, guanidinium chloride has been shown to "cure" prion positive yeast cells (i.e. cells exhibiting a prion positive phenotype revert to a prion negative phenotype). This is the result of inhibition of the Hsp104 chaperone protein known to play an important role in prion fiber fragmentation and propagation.

Historical survey Petrunkin and Petrunkin (1927, 1928) appear to be the first who studied the binding of GnHCl to gelatin and a mixture of thermally denatured protein from brain extract. Greenstein (1938, 1939), however, appears to be the first to discover the high denaturing action of guanidinium halides and thiocyanates in following the liberation of sulfhydryl groups in ovalbumin and other proteins as a function of salt concentration.

Medical uses Guanidine hydrochloride is indicated for the reduction of the symptoms of muscle weakness and easy fatigability associated with Lambert-Eaton myasthenic syndrome. It is not indicated for treating myasthenia gravis. It apparently acts by enhancing the release of acetylcholine following a nerve impulse. It also appears to slow the rates of depolarization and repolarization of muscle cell membranes. Initial dosage is usually between 10 and 15 mg/kg (5 to 7 mg/pound) of body weight per day in 3 or 4 divided doses. This dosage may be gradually increased to a total daily dosage of 35 mg/kg (16 mg/pound) of body weight per day or up to the development of side effects. Side effects may include increased peristalsis, diarrhea, paresthesia (tingling and numbness), and nausea. Fatal bone-marrow suppression, apparently dose related, can occur with guanidine.

References

Illustrations

Worked examples

Example 1 — a first encounter with Guanidinium chloride

Start with the simplest possible case. Write down what Guanidinium chloride claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 Guanidinium chloride 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 Guanidinium chloride 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 Guanidinium chloride

In research: Guanidinium chloride appears in chemistry 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 Guanidinium chloride 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: Guanidinium chloride is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chaotropic agents, Guanidinium compounds, Hydrochlorides, so understanding it makes those chapters shorter.
In everyday life: Look for Guanidinium chloride 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 Guanidinium chloride in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Guanidinium chloride 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 Guanidinium chloride out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Guanidinium chloride in simple terms?

Guanidinium chloride or guanidine hydrochloride, usually abbreviated GdmCl and sometimes GdnHCl or GuHCl, is the hydrochloride salt of guanidine. Structure Guanidinium chloride crystallizes in orthorhombic space group Pbca.

Why does Guanidinium chloride matter?

Because it connects several chemistry 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 Guanidinium chloride?

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 Guanidinium chloride.