(S)-lactic acid

CAS No. 79-33-4

Formula: C3H6O3
Basic Info

Lactic acid is an organic compound with the formula CH3CH(OH)CO2H. In its solid state, it is white and water-soluble. In its liquid state, it is clear. It is produced both naturally and synthetically. With a hydroxyl group adjacent to the carboxyl group, lactic acid is classified as an alpha-hydroxy acid (AHA). In the form of its conjugate base called lactate, it plays a role in several biochemical processes.
In solution, it can ionize a proton from the carboxyl group, producing the lactate ion CH 3CH(OH)CO− 2. Compared to acetic acid, its pKa is 1 unit less, meaning lactic acid deprotonates ten times more easily than acetic acid does. This higher acidity is the consequence of the intramolecular hydrogen bonding between the α-hydroxyl and the carboxylate group.
Lactic acid is chiral, consisting of two optical isomers. One is known as L-(+)-lactic acid or (S)-lactic acid and the other, its mirror image, is D-(−)-lactic acid or (R)-lactic acid. A mixture of the two in equal amounts is called DL-lactic acid, or racemic lactic acid.
Lactic acid is hygroscopic. DL-lactic acid is miscible with water and with ethanol above its melting point which is around 17 or 18°C. D-lactic acid and L-lactic acid have a higher melting point.
In animals, L-lactate is constantly produced from pyruvate via the enzyme lactate dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise. It does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal, which is governed by a number of factors, including monocarboxylate transporters, concentration and isoform of LDH, and oxidative capacity of tissues. The concentration of blood lactate is usually 1–2 mmol/L at rest, but can rise to over 20mmol/L during intense exertion and as high as 25mmol/L afterward.
In industry, lactic acid fermentation is performed by lactic acid bacteria, which convert simple carbohydrates such as glucose, sucrose, or galactose to lactic acid. These bacteria can also grow in the mouth; the acid they produce is responsible for the tooth decay known as caries.
In medicine, lactate is one of the main components of lactated Ringer's solution and Hartmann's solution. These intravenous fluids consist of sodium and potassium cations along with lactate and chloride anions in solution with distilled water, generally in concentrations isotonic with human blood. It is most commonly used for fluid resuscitation after blood loss due to trauma, surgery, or burns.

Formula
C3H6O3
Molecular Weight
90.0779
Exact Mass
90.0317
LogP
-0.5482
PSA
57.53
Synonyms

Propanoic acid, 2-hydroxy-, (S)-

L-(+)-Lactic acid

L(+)-Lactic acid

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Properties
Appearance & Physical State
crystalline solid
Density
1.206
Boiling Point
125ºC
Melting Point
52-54ºC
Flash Point
109.9ºC
Refractive Index
1.426-1.428
Water Solubility
SOLUBLE
Storage Condition
2-8ºC
Safety Info
RTECS
OD2800000
Safety Statements
S26-S36/37/39-S45
WGK Germany
1
Risk Statements
R34
HS Code
2918110000
RIDADR
UN 3261
Hazard Class
8
Packing Group
III
Caution Statement
P280; P305 + P351 + P338 + P310
Hazard Codes
Hazard Declaration
Spectrum
NMR Spectrum 1H NMR : Predict
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Mass Spectrum Mass spectrum (electron ionization)
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Analysis Methods
Normal alkane RI, polar column, temperature ramp
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Column Shape
Capillary
Active Phase(℃)
RTX-Wax
Retention index
2159.
Temperature Control
Method
temperature ramp
Comments
30. m/0.25 mm/0.5 μm, He, 40. C @ 5. min, 10. K/min, 220. C @ 10. min
Reference
Prososki, R.A.Etzel, M.R.Rankin, S.A.Solvent type affects the number, distribution, and relative quantities of volatile compounds found in sweet whey powderJ. Dairy Sci.2007, 90, 2, 523-531.

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