Lactose

Lactose (milk sugar)

Names
IUPAC name β-D-galactopyranosyl-(1→4)-D-glucose
Other names Milk sugar 4-O-β-D-galactopyranosyl-D-glucose
Identifiers
CAS Number	63-42-3 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:36218 Y
ChEMBL	ChEMBL417016 N
ChemSpider	5904 Y
ECHA InfoCard	100.000.509
EC Number	200-559-2
PubChem	6134
UNII	3SY5LH9PMK N
InChI InChI=1S/C12H22O11/c13-1-3-5(15)6(16)9(19)12(22-3)23-10-4(2-14)21-11(20)8(18)7(10)17/h3-20H,1-2H2/t3-,4-,5+,6+,7-,8-,9-,10-,11-,12+/m1/s1 Y Key: GUBGYTABKSRVRQ-DCSYEGIMSA-N Y InChI=1/C12H22O11/c13-1-3-5(15)6(16)9(19)12(22-3)23-10-4(2-14)21-11(20)8(18)7(10)17/h3-20H,1-2H2/t3-,4-,5+,6+,7-,8-,9-,10-,11-,12+/m1/s1 Key: GUBGYTABKSRVRQ-DCSYEGIMBP
SMILES C([C@@H]1[C@@H]([C@@H]([C@H]([C@@H](O1)O[C@@H]2[C@H](O[C@H]([C@@H]([C@H]2O)O)O)CO)O)O)O)O
Properties
Chemical formula	C12H22O11
Molar mass	342.30 g/mol
Appearance	white solid
Density	1.525 g/cm3
Melting point	202.8 °C (397.0 °F; 475.9 K)
Solubility in water	19.5 g/100 mL
Chiral rotation ([α]D)	+55.4°
Thermochemistry
Std enthalpy of combustion (ΔcHo298)	5652 kJ/mol, 1351 kcal/mol, 16.5 kJ/g, 3.94 kcal/g
Hazards
NFPA 704	0 1 0
Flash point	357.8 °C (676.0 °F; 631.0 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Lactose is a disaccharide sugar composed of galactose and glucose that is found in milk. Lactose makes up around 2–8% of milk (by weight), although the amount varies among species and individuals, and milk with a reduced amount of lactose also exists. It is extracted from sweet or sour whey. The name comes from lac (gen. lactis), the Latin word for milk, plus the -ose ending used to name sugars. It has a formula of C₁₂H₂₂O₁₁ and the hydrate formula C₁₂H₂₂O₁₁·H₂O, making it an isomer of sucrose.

The first crude isolation of lactose, by Italian physician Fabrizio Bartoletti (1576–1630), was published in 1633. In 1700, the Venetian pharmacist Lodovico Testi (1640–1707) published a booklet of testimonials to the power of milk sugar (saccharum lactis) to relieve, among other ailments, the symptoms of arthritis. In 1715, Testi's procedure for making milk sugar was published by Antonio Vallisneri. Lactose was identified as a sugar in 1780 by Carl Wilhelm Scheele.

In 1812, Heinrich Vogel (1778-1867) recognized that glucose was a product of hydrolyzing lactose. In 1856, Louis Pasteur crystallized the other component of lactose, galactose. By 1894, Emil Fischer had established the configurations of the component sugars.

Lactose was named by the French chemist Jean Baptiste André Dumas (1800-1884) in 1843.

Lactose is a disaccharide derived from the condensation of galactose and glucose, which form a β-1→4 glycosidic linkage. Its systematic name is β-D-galactopyranosyl-(1→4)-D-glucose. The glucose can be in either the α-pyranose form or the β-pyranose form, whereas the galactose can only have the β-pyranose form: hence α-lactose and β-lactose refer to the anomeric form of the glucopyranose ring alone.