Is Caffeine bigger than Theobromine?

Caffeine is the heavier molecule, 194.19 g/mol against 180.16 g/mol for Theobromine. Caffeine is C8H10N4O2 and Theobromine is C7H8N4O2.

Which has the lower reported LD50, Caffeine or Theobromine?

Caffeine, at 192 mg/kg (oral, rat), against 300 mg/kg (oral, dog) for Theobromine. An LD50 is one acute animal measurement, and the two here were not necessarily measured in the same species, so it is a data point rather than a ranking of how dangerous either is to a person.

Caffeine vs Theobromine: what is the difference?

Caffeine carries three methyl groups and theobromine two, so caffeine blocks adenosine far harder while theobromine acts more gently and lasts longer.

One methyl group apart.

CaffeineC8H10N4O2Highlighted: the extra methyl group and its nitrogen.

TheobromineC7H8N4O2Highlighted: the same nitrogen, with a hydrogen instead.

Sources and notes

The sentence under the titlefrom sourceMoleculeFinder comparison notesThe pair's answer line.
The two drawingscomputedMoleculeFinder rule (RDKit MCS)Drawn the same way round on the skeleton they share; the amber marks where the two differ.
The captionfrom sourceMoleculeFinder curated
What is highlightedfrom sourceMoleculeFinder curatedOne line under each drawing, written from the atoms the amber marks.
Structural similaritycomputedRDKit Morgan/Tanimoto0.53 of 1, a Morgan fingerprint Tanimoto coefficient. It measures shape, not effect.

Side by side

	Caffeine	Theobromine
Molecular weightCalculated PubChem	194.19 g/molC8H10N4O2	180.16 g/molC7H8N4O2
Hydrogen-bond donorsCalculated PubChem	0	1
Half-life in the bodyEditorial MoleculeFinder curated	about 5 h	about 7.2 h
Where each turns upEditorial MoleculeFinder food and product lists	CoffeeAbout 95 mg per 8 oz cupNaturally present Energy drinksAbout 80 mg per 250 ml canAdded by the maker TeaAbout 47 mg per 8 oz cupNaturally present Soft drinksAdded by the maker Also on our chocolate and cocoa lists	CoffeeNaturally present TeaNaturally present ChocolateAbout 150 to 250 mg per serving of dark chocolateNaturally present CocoaNaturally present
FamilyEditorial MoleculeFinder curated	Plant alkaloids, Stimulants	Plant alkaloids, Stimulants
Everyday groupEditorial MoleculeFinder curated	Food & flavor	Plant
Hazard labelReported ECHA, EU CLP Regulation, Safe Work Australia via PubChem; ECHA, HSDB via PubChem	Warning	Warning
The supplier-filed hazard label's signal word, not a statement about ordinary use.
Oral LD50Measured HSDB via PubChem	192 mg/kgpure caffeine, rat, oral	300 mg/kgpure theobromine, dog, oral
A single acute animal measure, here in two different species. It ranks nothing about human safety.

Sources and notes

Molecular weightcomputedPubChemComputed from the structure; the formula is under each weight.
Hydrogen-bond donorscomputedPubChemThe hydrogens on nitrogen or oxygen that each molecule can lend to a hydrogen bond, counted from its structure.
Half-life in the bodyfrom sourceMoleculeFinder curatedIn a typical adult: the time the body takes to clear half of it.
Where each turns upfrom sourceMoleculeFinder food and product listsEach amount is an editorial figure from our lists, not a measurement of any one product. Each mark is set by hand on the list, never inferred.
Familyfrom sourceMoleculeFinder curated
Everyday groupfrom sourceMoleculeFinder curated
Hazard labelfrom sourceECHA, EU CLP Regulation, Safe Work Australia via PubChem; ECHA, HSDB via PubChem
Oral LD50from sourceHSDB via PubChem
ECHAfrom sourceAttributionSource: European Chemicals Agency, echa.europa.eu.
EU CLP Regulationfrom sourceAttributionSource: EUR-Lex, Regulation (EC) No 1272/2008, © European Union.
Safe Work Australiafrom sourceAttributionSource: Safe Work Australia, Hazardous Chemical Information System, © Commonwealth of Australia, CC BY 4.0.
Identifiersfrom sourcePubChemPubChem CID 2519 (Caffeine) and 5429 (Theobromine).

In more detail

The two share one molecular skeleton, and that one methyl group is the whole of the C8H10N4O2 against C7H8N4O2 in the table. That one group changes how strongly each binds the brain's adenosine receptors, and caffeine binds far harder, which is why coffee arrives as a jolt and chocolate does not. Theobromine lingers longer instead, with a half-life around 7.2 hours against caffeine's 5, so cocoa's lift is slower and flatter. Both come from the same plants in different proportions: coffee and tea lead with caffeine, cocoa leads with theobromine. The reported oral LD50 also splits them, 192 mg/kg in rats for caffeine against 300 mg/kg in dogs for theobromine, and it is theobromine that dogs clear too slowly to tolerate.

Sources and notes

The paragraphfrom sourceMoleculeFinder comparison notes

Questions

What is the difference between Caffeine and Theobromine?: Caffeine carries three methyl groups and theobromine two, so caffeine blocks adenosine far harder while theobromine acts more gently and lasts longer.
Is Caffeine bigger than Theobromine?: Caffeine is the heavier molecule, 194.19 g/mol against 180.16 g/mol for Theobromine. Caffeine is C8H10N4O2 and Theobromine is C7H8N4O2.
Which has the lower reported LD50, Caffeine or Theobromine?: Caffeine, at 192 mg/kg (oral, rat), against 300 mg/kg (oral, dog) for Theobromine. An LD50 is one acute animal measurement, and the two here were not necessarily measured in the same species, so it is a data point rather than a ranking of how dangerous either is to a person.

Sources and notes

The answersfrom sourceMoleculeFinderThe first is the pair's answer line; the others are read off the table above.

Keep going

CaffeineIts structure, properties and sources, on its own page.TheobromineIts structure, properties and sources, on its own page.CoffeeFollow caffeine from your cup to the sleepiness signal it blocks, then on to chocolate.