Alanine

Ball-and-stick Stick Space-filling

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

13 atoms, 12 bonds.

IUPAC name: (2S)-2-aminopropanoic acid
Molar mass: 89.094(10) g/mol
Atoms: 13
SMILES: CC(C(=O)O)N
InChIKey: QNAYBMKLOCPYGJ-REOHCLBHSA-N
PubChem CID: 5950

Made of

Structural formula of alanine. Each unlabelled corner is a carbon atom, and the one hydrogen on carbon is 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.

Blood plasma carries alanine at high levels as a free molecule, not bound up in protein, according to MeSH, the Medical Subject Headings thesaurus. ChEBI, a database of biologically relevant small molecules, classes it as a proteinogenic amino acid, one of the set built into proteins. Its IUPAC name, (2S)-2-aminopropanoic acid, describes a three-carbon acid with an amine group, –NH₂, on its second carbon, next to the acid group. The (2S) prefix fixes one of two mirror-image arrangements at that carbon, and ChEBI identifies the form as the L-enantiomer.

Three carbon, seven hydrogen, one nitrogen and two oxygen atoms make up C₃H₇NO₂, with a molar mass of 89.09 g/mol. The Hazardous Substances Data Bank (HSDB) describes a white, odourless crystalline powder with a sweet taste. Some 164 g dissolve in a litre of water at 25 °C, yet the solid is insoluble in ether and acetone.

Structure and bonding

Alanine is built around one central carbon. Its four partners are a hydrogen, a methyl group (CH₃), an amine group (NH₂) and a carboxylic acid group (COOH). In Chem1’s amino-acid formula, R–CH(NH₂)COOH, alanine’s R is that lone methyl. With Labels on, the N sits on the central carbon and both O atoms on the carboxyl carbon.

Angles at the central carbon run from about 108° to 111°, near the tetrahedral arrangement Chem1 describes for carbon in most organic compounds. At the acid end the O=C–O angle opens to about 123°, and the Stick view shows the double bond as the shorter, 1.22 Å against 1.36 Å. In the Space-filling view the methyl hydrogens form one small rounded lobe.

The drawing shows the uncharged form, with a C=O and an O–H in the acid group and a neutral NH₂. ChEBI also records a zwitterion of L-alanine as its tautomer: the same atoms, with the amine and acid groups each carrying a charge. HSDB gives pK_a values, a measure of how easily a group gives up a hydrogen ion, of 2.34 for the acid and 9.69 for the amine. The model is also only the L form.

Where it turns up

Alanine reaches the kitchen through flavour chemistry. HSDB lists it in Maillard flavours for meat and poultry, and to a lesser extent in chocolate, cocoa, cream, butter and tobacco flavours. The US Food and Drug Administration (FDA) lists it as a flavouring agent, and L-alanine is permitted as a direct food additive. Personal-care products containing it number 33 in the Consumer Product Information Database, and it sits on the ingredient list of the Cosmetic Ingredient Review (CIR).

Protein is also a raw material for it. Splitting gelatin, silk or the protein zein apart with water releases alanine, a route HSDB lists for obtaining it. Some L-alanine is still isolated from these protein hydrolysates. Among plants, the LOTUS natural-products database records L-alanine in Euphorbia prostrata and Angelica gigas.

Why it matters

Cells make their own alanine. MeSH calls it non-essential and made from pyruvate by transamination, and it links alanine to sugar and acid metabolism and to energy for muscle, brain and the central nervous system. The US National Cancer Institute’s thesaurus counts it among the amino acids most widely used in building proteins. In proteins, hydrogen bonds from N–H groups in the amino parts to C=O groups in the acid parts shape the alpha helix and beta sheet, according to Chem1.

Manufacturing alanine turns on its handedness. HSDB reports that L-alanine is made industrially from L-aspartic acid by immobilised cells of the bacterium Pseudomonas dacunhae, and also through asymmetric hydrolysis by a microbial acylase. In direct fermentation, microbes usually yield a D,L mixture because of the alanine racemase they carry. A mutant of Arthrobacter oxydans lacking that enzyme turns glucose into L-alanine almost free of the D form. US Environmental Protection Agency (EPA) reporting put the national volume of L-alanine for 2023 at 10 million to under 50 million pounds.

Properties

Properties of alanine Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 5950.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₃H₇NO₂
Molar mass	89.094(10) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	3
Hydrogen atoms	7
Nitrogen atoms	1
Oxygen atoms	2
Bonds	12
Single bonds	11
Double bonds	1
PubChem molecular weight	89.09 g/mol	g/mol	PubChem

Safety

Alanine is essentially harmless in its everyday forms, as a building block of food proteins and a permitted food additive. Under the Globally Harmonized System (GHS) it is not classified, and 99% (294 of 297) of reports meet no GHS hazard criteria. The PubChem Laboratory Chemical Safety Summary is the reference sheet for it.

Questions

What does the 3D model of alanine show?

It shows one L-alanine molecule, 13 atoms joined by 12 bonds. A central carbon holds a hydrogen, a methyl group, an amine group and a carboxylic acid group, the last drawn with one C=O double bond and one C–O–H. The angles at that carbon sit near 109°. The drawing is the neutral form, although ChEBI also records a zwitterion tautomer in which two groups carry charges.

Is alanine an essential amino acid?

No. MeSH classes alanine as non-essential, since the body produces it from pyruvate by transamination. NHGRI keeps the word essential for amino acids the body cannot synthesise, which then have to come from the diet. HSDB classes it as non-essential for maintaining growth in rats. The FDA files it under the pharmacologic class Amino Acid.

What is the difference between L-alanine and D-alanine?

ChEBI calls them enantiomers, a pair of mirror-image forms with the same atoms and the same bonds. L-alanine, the (2S) form of the IUPAC name, is the one ChEBI lists as a proteinogenic amino acid, and it is the one the 3D model draws. HSDB gives it a specific optical rotation of +2.42° at 25 °C, measured in water with the sodium D line.

What is alanine used for?

Haz-Map, citing HSDB and the FDA, lists microbiological and biochemical research, dietary supplements and flavouring, and HSDB also records it as a medication. In US EPA chemical data reporting, industry records L-alanine as an intermediate used to make other chemicals, and the NORMAN network classes its cosmetic role as antistatic.

Made of the same elements

C₂H₅NO₂ Glycine 10 atoms, 9 bonds.
C₅H₆N₂O₂ Thymine 15 atoms, 15 bonds.
C₄H₄N₂O₂ Uracil 12 atoms, 12 bonds.
C₄H₅N₃O Cytosine 13 atoms, 13 bonds.
C₅H₉NO₄ Glutamic acid 19 atoms, 18 bonds.
C₈H₉NO₂ Acetaminophen 20 atoms, 20 bonds.
CO(NH₂)₂ Urea 8 atoms, 7 bonds.
C₈H₁₁NO₂ Dopamine 22 atoms, 22 bonds.

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

C₅H₅N₅O Guanine 16 atoms, 17 bonds.
C₆H₁₃NO₂ Isoleucine 22 atoms, 21 bonds.
C₆H₁₃NO₂ Leucine 22 atoms, 21 bonds.
C₅H₄N₄O₃ Uric acid 16 atoms, 17 bonds.
C₉H₁₁NO₂ Phenylalanine 23 atoms, 23 bonds.
C₈H₁₀N₄O₂ Caffeine 24 atoms, 25 bonds.
C₉H₁₁NO₃ Tyrosine 24 atoms, 24 bonds.
C₉H₁₃NO₃ Epinephrine 26 atoms, 26 bonds.
C₁₀H₁₂N₂O Serotonin 25 atoms, 26 bonds.
C₁₁H₁₂N₂O₂ Tryptophan 27 atoms, 28 bonds.
C₁₂H₁₇NO DEET 31 atoms, 31 bonds.
C₁₃H₁₆N₂O₂ Melatonin 33 atoms, 34 bonds.
C₁₃H₂₁NO₃ Albuterol 38 atoms, 38 bonds.
C₁₄H₁₈N₂O₅ Aspartame 39 atoms, 39 bonds.
C₁₄H₂₂N₂O Lidocaine 39 atoms, 39 bonds.
C₁₇H₂₁NO Diphenhydramine 40 atoms, 41 bonds.
C₂₀H₂₄N₂O₂ Quinine 48 atoms, 51 bonds.