Salicylic acid

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Salicylic acid
Chemical name	2-Hydroxybenzoic acid
Chemical formula	C₇H₆O₃
Molecular mass	138.12 g/mol
Melting point	159 °C
Boiling point	?
Density	1.44 g/cm³ (at 20 °C)
pKa	2.97
CAS number	[69-72-7]
SMILES	C1(O)=CC=CC=C1C(O)=O
Image:Salicylic acid chemical structure.png
Disclaimer and references

Salicylic acid is a colorless, crystalline organic carboxylic acid. It is usually prepared by Kolbe synthesis (aka Kolbe-Schmitt reaction). Salicylic acid functions as a plant hormone.

Salicylic acid is toxic if ingested in large quantities, but in small quantities is used as a food preservative and antiseptic in toothpaste. The carboxyl group (–COOH) can react with alcohols, forming several useful esters. The ester with methanol is methyl salicylate, also known under the name oil of wintergreen. The hydroxyl group (–OH) can be acetylated to form acetylsalicylic acid (aspirin). Salicylic acid can also trap oxygen (O₂) and initiate free radical reactions.

Salicylic acid is the key additive in many skin-care products for the treatment of acne, callouses and corns, keratosis pilaris and warts. It treats acne by causing skin cells to slough off more readily, preventing pores from clogging up.

The medicinal properties of salicylate (mainly the lowering of fever) have been known since ancient times. The substance occurs in the bark of willow trees and the name Salicylic acid is derived from the Latin name for the Willow tree - Salix.

Image:Aspirin.jpg

Acetylsalicylic acid (Aspirin or ASA) can be prepared by the esterification of the phenolic hydroxyl group of salicylic acid.

1 Salicylic acid as a plant hormone
- 1.1 Location, characteristics and occasions for synthesis induction
- 1.2 Effects
2 See also
3 References

Salicylic acid as a plant hormone

Here is a list of some of salicylic acid's properties when acting as a plant hormone. It is interesting to note, in light of these properties, that there is a popular belief that cut flowers will last longer if aspirin (acetylsalicylic acid) is dissolved in their water.

Location, characteristics and occasions for synthesis induction

Cells returning from water stress
Released by cells secure in having more than enough nutrients and environmental conditions locally to survive at its current metabolic level
All cells capable of synthesizing
Has its effect or acts by rapid local increases followed by rapid decreases in levels

Effects

Retards senescence (regulatory role) – probably by inhibiting Ethylene biosynthesis
Induces flowering
Inhibits seed germination – by inhibiting ABA synthesis
May also block the wound response and act antagonistically to ABA – preventing the wound response from spreading further than necessary
After a survival threat has passed SA quickly removes a plant, organ, tissue or cell from a defensive posture and returns it to normal functioning
Increases cell metabolism rate to take advantage of new complete more advantageous nutrient and environmental conditions
A climactic or sustained level of SA may occur if a cell has reached its peak metabolic levels and may signal that a plant's resources can be turned to growth
This climactic or sustained level of SA may be a prerequisite for the synthesis of Auxin and/or Cytokinin, because only then does a plant know that it has enough resources to turn them to growing bigger