indoleacetic acid

Indole-3-acetic acid
IUPAC name	2-(1H-indol-3-yl)acetic acid
Other names	Indole-3-acetic acid, indolylacetic acid, indoleacetic acid, heteroauxin, IAA
Identifiers
CAS number	87-51-4 Y
PubChem	802
SMILES	C1=CC=C2C(=C1) C(=CN2)CC(=O)O
ChemSpider ID	780
Properties
Molecular formula	C10H9NO2
Molar mass	175.184
Appearance	white solid
Melting point	168-170 °C (441-443 K)
Solubility in water	moderate
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Indole-3-acetic acid, also known as IAA, is a heterocyclic compound that is an phytohormone called auxins. This colourless solid is probably the most important plant auxin. The molecule is derived from indole, containing a carboxymethyl group (acetic acid).

Synthesis

IAA is produced in cells in the apex (bud) and young leaves of a plant. Plant cells mainly synthesize IAA from tryptophan but can also produce it independently of tryptophan.

Chemically, it can be synthesized by the reaction of indole with glycolic acid in the presence of base at 250 °C:^[1]

Many methods for its synthesis have been developed since its original synthesis from indole-3-acetonitrile.^[2]

Bioactivity and related compounds

IAA has many different effects, as all auxins do, such as inducing cell elongation and cell division with all subsequent results for plant growth and development. There are less expensive and metabolically stable synthetic auxin analogs on the market for use in horticulture, such as indole-3-butyric acid (IBA) and 1-naphthaleneacetic acid (NAA).^{[citation needed]}

Studies of IAA in the 1940s led to the development of the phenoxy herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Like IBA and NAA, 2,4-D and 2,4,5-T are metabolically and environmentally more stable analogs of IAA. However, when sprayed on broad-leaf dicot plants, they induce rapid, uncontrolled growth, eventually killing them. First introduced in 1946, these herbicides were in widespread use in agriculture by the middle of the 1950s.

References