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The Chemistry of Caffeine

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Chemists in a Big World

         My Chemists in a Big World is all about the chemistry of Caffeine and the way it effects the human body. Caffeine is the common name for trimethylxanthine, this chemical is also known as coffeine, theine, mateine, guaranine, or methyltheobromine and is found commonly in coffee, tea, and guarana. This chemical is put in energy drinks and sodas to give them a bitter edge and to give the physical and psychological boost to drinkers.

Caffeine is an ergogenic: increasing the capacity for mental or physical labor. Many studies have been conducted proving the capacity caffeine has to help athletic endurance, energy, speed, and mental prowess. Caffeine is often in headache medicines to increase their effectiveness and to counteract antihistamines that may be in them. 

Caffeine is completely absorbed into the stomach and small intestines within forty five minutes of ingestion. It is a xanthine alkaloid that acts as a stimulant in humans and is very toxic to household pets such as dogs and cats.

        Caffeine has been consumed around the world in its many different forms for thousands of years. Many people today wouldn't be able to function in the morning without there morning brew. People come to have caffeine based addictions and can have headaches and become sick from withdrawal. Caffeine has been America's wonder drug for years and will continue to be for many years to come.

What is caffeine and how does it work website

What Is Caffeine and How Does It Work?

Caffeine (C8H10N4O2) is the common name for trimethylxanthine (systematic name is 1,3,7-trimethylxanthine or 3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione). The chemical is also known as coffeine, theine, mateine, guaranine, or methyltheobromine. Caffeine is naturally produced by several plants, including coffee beans, guarana, yerba maté, cacao beans, and tea. For the plants, caffeine acts as a natural pesticide. It paralyzes and kills insects that attempt to feed on the plants. The molecule was first isolated by the German chemist Friedrich Ferdinand Runge in 1819. 

When purified, caffeine is an intensely bitter white powder. It is added to colas and other soft drinks to impart a pleasing bitter note. However, caffeine is also an addictive stimulant. In humans, it stimulates the central nervous system, heart rate, and respiration, has psychotropic (mood altering) properties, and acts as a mild diuretic. 

A normal dose of caffeine is generally considered to be 100 mg, which is roughly the amount found in a cup of coffee. However, more than half of all American adults consume more than 300 mg of caffeine every day, which makes it America's most popular drug. Caffeine is generally consumed in coffee, cola, chocolate, and tea, although it is also available over-the-counter as a stimulant. 

Caffeine is believed to work by blocking adenosine receptors in the brain and other organs. This reduces the ability of adenosine to bind to the receptors, which would slow down cellular activity. The stimulated nerve cells release the hormone epinephrine (adrenaline), which increases heart rate, blood pressure, and blood flow to muscles, decreases blood flow to the skin and organs, and causes the liver to release glucose. Caffeine also increases levels of the neurotransmitter dopamine. 

Caffeine is quickly and completely removed from the brain. Its effects are short-lived and it tends not to negatively affect concentration or higher brain functions. However, continued exposure to caffeine leads to developing a tolerance to it. Tolerance causes the body to become sensitized to to adenosine, so withdrawal causes blood pressure to drop, which can result in a headache and other symptoms. Too much caffeine can result in caffeine intoxication, which is characterized by nervousness, excitement, increased urination, insomnia, flushed face, cold hands/feet, intestinal complaints, and sometimes hallucinations. Some people experience the symptoms of caffeine intoxication after ingesting as little as 250 mg per day. The lethal ingested dose, for an adult person, is estimated to be 13-19 grams. While generally considered safe for people, caffeine can be very toxic to household pets, such as dogs, horses, or parrots. Caffeine intake has been demonstrated to reduce the risk of type II diabetes mellitus. In addition to use as a stimulant and flavoring agent, caffeine is included in many over-the-counter headache remedies.


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For other uses, see Caffeine (disambiguation).

Caffeine is a xanthine alkaloid compound that acts as a stimulant in humans. Caffeine is sometimes called guaranine when found in guarana, mateine when found in mate, and theine when found in tea. It is found in the leaves and beans of the coffee plant, in tea, yerba mate, and guarana berries, and in small quantities in cocoa, the kola nut and the Yaupon Holly. Overall, caffeine is found in the beans, leaves, and fruit of over 60 plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding upon them.

Caffeine is a central nervous system (CNS) stimulant, having the effect of temporarily warding off drowsiness and restoring alertness. Beverages containing caffeine, such as coffee, tea, soft drinks and energy drinks enjoy great popularity: caffeine is the world's most widely consumed psychoactive substance. In North America, 90% of adults consume caffeine daily.[1]

Many natural sources of caffeine also contain widely varying mixtures of other xanthine alkaloids, including the cardiac stimulants theophylline and theobromine and other substances such as tannins.



Caffeine has a significant effect on spiders, which is reflected in their web construction

Caffeine is a central nervous system and metabolic stimulant,[20] and is used both recreationally and medically to reduce physical fatigue and restore mental alertness when unusual weakness or drowsiness occurs. Caffeine stimulates the central nervous system first at the higher levels, resulting in increased alertness and wakefulness, faster and clearer flow of thought, increased focus, and better general body coordination, and later at the spinal cord level at higher doses.[21] The precise amount of caffeine necessary to produce effects varies from person to person depending on body size and degree of tolerance to caffeine. It takes less than an hour for caffeine to begin affecting the body and a mild dose wears off in three to four hours.[21] Consumption of caffeine does not eliminate the need for sleep: it only temporarily reduces the sensation of being tired.

With these effects, caffeine is an ergogenic: increasing the capacity for mental or physical labor. A study conducted in 1979 showed a 7% increase in distance cycled over a period of two hours in subjects who consumed caffeine compared to control tests.[22] Other studies attained much more dramatic results; one particular study of trained runners showed a 44% increase in "race-pace" endurance, as well as a 51% increase in cycling endurance, after a dosage of 9 milligrams of caffeine per kilogram of body weight.[23] The extensive boost shown in the runners is not an isolated case; additional studies have reported similar effects. Another study found 5.5 milligrams of caffeine per kilogram of body mass resulted in subjects cycling 29% longer during high intensity circuits.[24]

Caffeine is sometimes administered in combination with medicines to increase their effectiveness. Caffeine makes pain relievers 40% more effective in relieving headaches and helps the body absorb headache medications more quickly, bringing faster relief.[25] For this reason, many over-the-counter headache drugs include caffeine in their formula. It is also used with ergotamine in the treatment of migraine and cluster headaches as well as to overcome the drowsiness caused by antihistamines.

Breathing problems in premature infants, apnea of prematurity, are sometimes treated with citrated caffeine, which is available only by prescription in many countries.[26] A reduction in bronchopulmonary dysplasia has been exhibited in premature infants treated with caffeine citrate therapy regimens. It is speculated that this reduction in bronchopulmonary dysplasia is tied to a reduction in exposure to positive airway pressure. [citation needed] The only short term risk associated with this treatment is a temporary reduction in weight gain during the therapy.[27]

While relatively safe for humans, caffeine is considerably more toxic to some other animals such as dogs, horses and parrots due to a much poorer ability to metabolize this compound. Caffeine has a much more significant effect on spiders, for example, than most other drugs do.[28]





Caffeine is metabolized in the liver into three primary metabolites: paraxanthine (84%), theobromine (12%), and theophylline (4%)

Caffeine is completely absorbed by the stomach and small intestine within 45 minutes of ingestion. After ingestion it is distributed throughout all tissues of the body and is eliminated by first-order kinetics.[41]

The half-life of caffeine — the time required for the body to eliminate one-half of the total amount of caffeine consumed at a given time — varies widely among individuals according to such factors as age, liver function, pregnancy, some concurrent medications, and the level of enzymes in the liver needed for caffeine metabolism. In healthy adults, caffeine's half-life is about 3-4 hours. In women taking oral contraceptives this is increased to around 13 hours, and in pregnant women the half-life is 18-20 hours. Caffeine can accumulate in individuals with severe liver disease when its half-life can increase to 96 hours.[42] In infants and young children, the half-life may be longer than in adults; half-life in a newborn baby may be as long as 30 hours. Other factors such as smoking can shorten caffeine's half-life.[43]

Caffeine is metabolized in the liver by the cytochrome P450 oxidase enzyme system (specifically, the 1A2 isozyme) into three metabolic dimethylxanthines,[44] which each have their own effects on the body:

Paraxanthine (84%) – Has the effect of increasing lipolysis, leading to elevated glycerol and free fatty acid levels in the blood plasma

Theobromine (12%) – Dilates blood vessels and increases urine volume. Theobromine is also the principal alkaloid in cocoa, and therefore chocolate

Theophylline (4%) – Relaxes smooth muscles of the bronchi, and is used to treat asthma. The therapeutic dose of theophylline, however, is many times greater than the levels attained from caffeine metabolism. 

Each of these metabolites is further metabolized and then excreted in the urine.


Mechanism of action


Caffeine's principal mode of action is as an antagonist of adenosine receptors in the brain. They are presented here side by side for comparison.

The principal mode of action of caffeine is as an antagonist of adenosine receptors in the brain.[45] The caffeine molecule is structurally similar to adenosine, and binds to adenosine receptors on the surface of cells without activating them (a "false transmitter" method of antagonism). The reduction in adenosine activity results in increased activity of the neurotransmitter dopamine, largely accounting for the stimulatory effects of caffeine. Caffeine can also increase levels of epinephrine/adrenaline,[46] possibly via a different mechanism. Acute usage of caffeine also increases levels of serotonin, causing positive changes in mood.

The inhibition of adenosine may be relevant in its diuretic properties. Because adenosine is known to constrict preferentially the afferent arterioles of the glomerulus, its inhibition may cause vasodilation, with an increase in renal blood flow (RBF) and glomerular filtration rate (GFR). This effect, called competitive inhibition, interrupts a pathway that normally serves to regulate nerve conduction by suppressing post-synaptic potentials. The result is an increase in the levels of epinephrine and norepinephrine/noradrenaline released via the hypothalamic-pituitary-adrenal axis.[47] Epinephrine, the natural endocrine response to a perceived threat, stimulates the sympathetic nervous system, leading to an increased heart rate, blood pressure and blood flow to muscles, a decreased blood flow to the skin and inner organs and a release of glucose by the liver.

Caffeine is also a known competitive inhibitor of the enzyme cAMP-phosphodiesterase (cAMP-PDE), which converts cyclic AMP (cAMP) in cells to its noncyclic form, allowing cAMP to build up in cells. Cyclic AMP participates in the messaging cascade produced by cells in response to stimulation by epinephrine, so by blocking its removal caffeine intensifies and prolongs the effects of epinephrine and epinephrine-like drugs such as amphetamine, methamphetamine, or methylphenidate. Increased concentrations of cAMP in parietal cells causes an increased activation of protein kinase A (PKA) which in turn increases activation of H+/K+ ATPase, resulting finally in increased gastric acid secretion by the cell.

The metabolites of caffeine contribute to caffeine's effects. Theobromine is a vasodilator that increases the amount of oxygen and nutrient flow to the brain and muscles. Theophylline, the second of the three primary metabolites, acts as a smooth muscle relaxant that chiefly affects bronchioles and acts as a chronotrope and inotrope that increases heart rate and efficiency. The third metabolic derivative, paraxanthine, is responsible for an increase in the lipolysis process, which releases glycerol and fatty acids into the blood to be used as a source of fuel by the muscles.[48]

From top to bottom:

Effect caffeine has on spiders

Metabolism breakdown of caffeine

caffeine composition




The wikipedia Site with this and other information





Systematic name


Other names

1,3,7-trimethylxanthine, trimethylxanthine,

theine, mateine, guaranine,


Molecular formula




Molar mass

194.19 g mol−1


Odorless, white needles or powder

CAS number



Density and phase

1.2 g/cm³, solid

Solubility in water

Slightly soluble

Other solvents

Soluble in ethyl acetate, chloroform, pyrimidine, pyrrole, tetrahydrofuran solution; moderately soluble in alcohol, accetone; slightly soluble in petroleum ether, ether, benzene.

Melting point

237 °C

Boiling point

178 °C (sublimes)

Acidity (pKa)

10.4 (40 °C)



External MSDS

Main hazards

May be fatal if inhaled, swallowed

or absorbed through the skin.

NFPA 704






Flash point


RTECS number


Except where noted otherwise, data are given for

materials in their standard state (at 25 °C, 100 kPa)

Infobox disclaimer and references


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