2-Methyl-2,4-pentanediol

2-Methyl-2,4-pentanediol (MPD) is an organic compound with the formula (CH₃)₂C(OH)CH₂CH(OH)CH₃. This colourless liquid is a chiral diol. It is produced industrially from diacetone alcohol by hydrogenation.^[4] Total European and USA production was 15000 tonnes in 2000.^[5]

2-Methyl-2,4-pentanediol

Names
Preferred IUPAC name 2-Methylpentane-2,4-diol
Other names 2-Methyl-2,4-pentanediol Hexylene glycol Diolane 1,1,3-Trimethyltrimethylenediol 2,4-Dihydroxy-2-methylpentane Isol
Identifiers
CAS Number	107-41-5 Y 99210-90-9 (R) N 99210-91-0 (S) N
3D model (JSmol)	Interactive image
Abbreviations	MPD
Beilstein Reference	1098298
ChEBI	CHEBI:62995 N
ChEMBL	ChEMBL2104293 N
ChemSpider	7582 Y
ECHA InfoCard	100.003.173
EC Number	203-489-0
PubChem CID	7870
RTECS number	SA0810000
UNII	KEH0A3F75J Y
UN number	1993
CompTox Dashboard (EPA)	DTXSID5021885
InChI InChI=1S/C6H14O2/c1-5(7)4-6(2,3)8/h5,7-8H,4H2,1-3H3 N Key: SVTBMSDMJJWYQN-UHFFFAOYSA-N N
SMILES CC(CC(C)(C)O)O
Properties
Chemical formula	C6H14O2
Molar mass	118.176 g·mol−1
Appearance	colourless liquid
Odor	mild, sweetish[1]
Density	0.92 g/mL
Melting point	−40 °C (−40 °F; 233 K)
Boiling point	197 °C (387 °F; 470 K)
Solubility in water	miscible[1]
Vapor pressure	0.05 mmHg (20°C)[1]
Hazards
GHS labelling:[2]
Pictograms
Signal word	Warning
Hazard statements	H315, H319
Precautionary statements	P264, P264+P265, P280, P302+P352, P305+P351+P338, P321, P332+P317, P337+P317, P362+P364
Flash point	98.3 °C (208.9 °F; 371.4 K)[3]
Explosive limits	1.3%-7.4%[1]
NIOSH (US health exposure limits):
PEL (Permissible)	none[1]
REL (Recommended)	C 25 ppm (125 mg/m3)[1]
IDLH (Immediate danger)	N.D.[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

2-Methyl-2,4-pentanediol exists as two enantiomers, (4R)-(−) and (4S)-(+). In the Protein Data Bank, the 3-letter code "MPD" refers to the (S)-(−) enantiomer, while "MRD" is used to refer to the (R)-(+) version. Commercial products labeled "MPD" are usually the racemate,^[6] also sold as and referred to as "hexylene glycol".^[7][8]

Uses

2-Methyl-2,4-pentanediol exhibits both surfactant and emulsion-stabilizing properties. Its relatively high viscosity and low volatility are advantageous in coatings, cleansers, cosmetics, solvents, lubricants, and hydraulic fluids.^[9] Although it is an irritant at higher concentrations, it is sometimes used in skin care, hair care, soap, and eye cosmetic products at concentrations ranging from 0.1% - 25%.^[10][11]

It is biodegradable and unlikely to accumulate in the environment.^[12]

Laboratory uses

In the laboratory it is a common precipitant and cryoprotectant in protein crystallography.^[13] Since hexylene glycol is compatible with polar and nonpolar molecules, it competes with the solvent in a crystallography experiment causing the protein to precipitate.^[14] Hexylene glycol is so effective in protein crystallography because its amphiphilic nature and small, flexible structure allows it to bind to many different locations on a protein secondary structure including alpha helices and beta sheets.^[15] When hexylene glycol binds to these different locations, water is removed and the protein crystals anneal, which prevents ice formation during cryocrystallography techniques.^[16] Incorporation of hexylene glycol into solution has been known to improve the resolution of X-ray diffraction making protein structures easily identifiable.^[17] Additionally hexylene glycol is not a strong denaturing agent and thus does not significantly alter the structure of a protein during the crystallography procedure.^[15]

Hexylene glycol is also used as a lubricant for polishing specimens in metallography.^[18]

Like related diols, it forms borate esters.