CID 134601

C₁₄H₁₈N₂O₅

Aspartame

C 14
H 18
N 2
O 5

Ball-and-stick Stick Space-filling

Drag to rotate; pinch or Ctrl + scroll to zoom. Arrow keys rotate, + − zoom, R resets.

39 atoms, 39 bonds.

IUPAC name: (3S)-3-amino-4-[[(2S)-1-methoxy-1-oxo-3-phenylpropan-2-yl]amino]-4-oxobutanoic acid
Molar mass: 294.307(39) g/mol
Atoms: 39
SMILES: COC(=O)C(CC1=CC=CC=C1)NC(=O)C(CC(=O)O)N
InChIKey: IAOZJIPTCAWIRG-QWRGUYRKSA-N
PubChem CID: 134601

Made of

C H N O

Structural formula of aspartame. Each unlabelled corner is a carbon atom, and the 11 hydrogens on carbon are not drawn. Wedges come toward you, hashes go back. It shows which atoms are joined to which, not the shape. The model above shows the shape.

Two amino acids and a methyl group make up aspartame. The US Food and Drug Administration (FDA) puts its sweetness at about 200 times that of table sugar, sucrose. The US Hazardous Substances Data Bank (HSDB) gives about 180 times, and about 160 times in a water solution. ChEBI, a database of chemicals that matter to biology, describes the molecule as a dipeptide. In it the alpha-carboxyl group of L-aspartic acid, the one on the same carbon as its amino group, is joined to the amino group of L-phenylalanine’s methyl ester.

Its IUPAC name, (3S)-3-amino-4-[[(2S)-1-methoxy-1-oxo-3-phenylpropan-2-yl]amino]-4-oxobutanoic acid, spells out the same pieces, and its molar mass is 294.3 g/mol. Handedness decides the taste: according to HSDB, both amino acids must keep the L configuration for the product to be sweet. Joining them chemically yields sweet alpha-aspartame alongside a non-sweet beta form, whereas an enzymatic process yields only the alpha form. The pure compound is a white, odourless, crystalline powder.

Structure and bonding

Aspartame’s 39 atoms are 14 carbon, 18 hydrogen, two nitrogen and five oxygen. A six-carbon ring sits at one end of the branched chain and a –COOH group at the other. Of the three C=O double bonds in Ball-and-stick, the mid-chain one has its carbon bonded to an N–H. That pair is the peptide bond, an amide link where the acid group of one amino acid has joined the amino group of the next.

The ring is drawn with single and double bonds in turn, a drawing convention the benzene page unpicks; turned edge-on in Stick view, the ring lies flat. The model draws the uncharged form, though ChEBI records a zwitterion form of aspartame as well, its amino group positive and its carboxyl group negative.

Two carbons, one bearing –NH₂ and one bearing the ring’s CH₂ arm, are chiral centres, and the IUPAC name fixes both as S. Space-filling buries the bonds inside one continuous surface of full-size atoms.

Where it turns up

FDA’s first regulation for aspartame came in 1974. It covered tabletop use and use in chewing gum, in cold breakfast cereals and in the dry bases of some foods. That 1974 decision also required foods sweetened with it that held no other protein to carry the statement “contains protein”. Its approved uses grew afterwards, most recently in 1996 to a general-purpose sweetener. FDA lists it as a flavour enhancer and a non-nutritive sweetener.

The United States, Canada and South Africa permit it in carbonated drinks. Like other sweeteners, it goes into foods and drinks sold as “sugar-free” or “diet”. Shoppers know it under names such as Nutrasweet, Equal, Sugar Twin and Canderel. The tabletop product is spray-dried with partly hydrolysed corn starch, starch already split in part by water. Two other sweeteners, neotame and advantame, are derived from it.

Why it matters

Water undoes aspartame, and its sweetness goes with it. In acid, the ester and amide bonds split, leaving the two amino acids. In neutral or alkaline solution the dipeptide closes instead into an unsweet ring, a diketopiperazine. Stability counts especially in fizzy and still drinks stored for months; aspartame keeps best between pH 4 and 5, and light speeds its breakdown.

In the gut, enzymes called esterases remove the methyl group as methanol, later oxidised to carbon dioxide, and dipeptidases split what remains. Much of the aspartic acid ends as carbon dioxide via the tricarboxylic acid cycle. Phenylalanine mostly joins body protein, either unchanged or as tyrosine.

After a June 2023 meeting, the International Agency for Research on Cancer classed aspartame in Group 2B, citing limited evidence of a link with liver cancer in people. JECFA, the food-additive committee of the Food and Agriculture Organization and the World Health Organization, concluded that year that eating it had not been shown to cause adverse effects. It found no mechanism by which aspartame could cause cancer.

Properties

Properties of aspartame Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 134601.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₁₄H₁₈N₂O₅
Molar mass	294.307(39) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	14
Hydrogen atoms	18
Nitrogen atoms	2
Oxygen atoms	5
Bonds	39
Single bonds	33
Double bonds	6
PubChem molecular weight	294.3 g/mol	g/mol	PubChem

Safety

Under its approved conditions of use, aspartame raises no safety concerns for FDA scientists, and it carries no Globally Harmonized System (GHS) hazard classification. The Scientific Committee on Food reconfirmed its safety in 2002, and FDA in 2007 saw no reason to change its view that aspartame is a safe general-purpose sweetener. Haz-Map lists it as an eye and mucous membrane irritant. The PubChem Laboratory Chemical Safety Summary for aspartame gathers these classifications.

Questions

Does aspartame cause cancer?

In June 2023 the International Agency for Research on Cancer placed aspartame in Group 2B. The US National Cancer Institute describes that group as limited evidence in humans or convincing evidence in animals, but not both. FDA replied that the classification does not tie aspartame to cancer, pointing to significant shortcomings in the studies. Among large cohort studies, NutriNet-Santé found higher consumers slightly more likely to develop cancer; others showed no clear association.

Why does aspartame come with a phenylketonurics warning?

Under the US regulation 21 CFR 172.804, any food containing aspartame must carry the label statement 'PHENYLKETONURICS: CONTAINS PHENYLALANINE', a condition meant to assure its safe use. FDA's stated aim is to let people with phenylketonuria (PKU) know that phenylalanine is present. The phenylalanine comes from digestion: the body metabolises aspartame as phenylalanine and aspartic acid, its two building blocks.

Why is aspartame not used in baking?

Heat costs aspartame its sweetness. FDA describes it as not heat stable, which is why it is typically left out of baked goods. Under 21 CFR 172.804, labels on the tabletop form carry instructions against using it in cooking or baking. The same regulation still allows it in baked goods when other approved baking additives are used with it to keep it working as a sweetener in the finished product.

Does aspartame have calories?

Some, though little in practice. Aspartame contains calories, FDA states, but since it tastes about 200 times as sweet as table sugar, people are likely to use less of it. Unlike some other intense sweeteners, it is metabolised in the body and so has some nutritive value, the Hazardous Substances Data Bank notes. The small quantity actually eaten, though, has a minimal nutritive effect.

Made of the same elements

C₁₃H₁₆N₂O₂ Melatonin 33 atoms, 34 bonds.
C₁₃H₂₁NO₃ Albuterol 38 atoms, 38 bonds.
C₁₂H₁₇NO DEET 31 atoms, 31 bonds.
C₁₄H₂₂N₂O Lidocaine 39 atoms, 39 bonds.
C₁₇H₂₁NO Diphenhydramine 40 atoms, 41 bonds.
C₁₁H₁₂N₂O₂ Tryptophan 27 atoms, 28 bonds.
C₉H₁₃NO₃ Epinephrine 26 atoms, 26 bonds.
C₁₀H₁₂N₂O Serotonin 25 atoms, 26 bonds.

All 25 compounds made of carbon, hydrogen, nitrogen and oxygen

C₂₀H₂₄N₂O₂ Quinine 48 atoms, 51 bonds.
C₉H₁₁NO₃ Tyrosine 24 atoms, 24 bonds.
C₉H₁₁NO₂ Phenylalanine 23 atoms, 23 bonds.
C₈H₁₁NO₂ Dopamine 22 atoms, 22 bonds.
C₆H₁₃NO₂ Isoleucine 22 atoms, 21 bonds.
C₆H₁₃NO₂ Leucine 22 atoms, 21 bonds.
C₈H₉NO₂ Acetaminophen 20 atoms, 20 bonds.
C₈H₁₀N₄O₂ Caffeine 24 atoms, 25 bonds.
C₅H₉NO₄ Glutamic acid 19 atoms, 18 bonds.
C₅H₆N₂O₂ Thymine 15 atoms, 15 bonds.
C₃H₇NO₂ Alanine 13 atoms, 12 bonds.
C₄H₄N₂O₂ Uracil 12 atoms, 12 bonds.
C₅H₄N₄O₃ Uric acid 16 atoms, 17 bonds.
C₄H₅N₃O Cytosine 13 atoms, 13 bonds.
C₂H₅NO₂ Glycine 10 atoms, 9 bonds.
C₅H₅N₅O Guanine 16 atoms, 17 bonds.
CO(NH₂)₂ Urea 8 atoms, 7 bonds.