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
3D model (JSmol)
Abbreviations MPD
1098298
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.003.173 Edit this at Wikidata
EC Number
  • 203-489-0
RTECS number
  • SA0810000
UNII
UN number 1993
  • InChI=1S/C6H14O2/c1-5(7)4-6(2,3)8/h5,7-8H,4H2,1-3H3 ☒N
    Key: SVTBMSDMJJWYQN-UHFFFAOYSA-N ☒N
  • CC(CC(C)(C)O)O
Properties
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)
miscible[1]
Vapor pressure 0.05 mmHg (20°C)[1]
Hazards
GHS labelling:[3]
GHS07: Exclamation mark
Warning
H315, H319
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)[2]
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 checkY☒N ?)

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 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.

References

  1. ^ a b c d e f g NIOSH Pocket Guide to Chemical Hazards. "#0328". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ CDC - NIOSH Pocket Guide to Chemical Hazards
  3. ^ "Hexylene Glycol". pubchem.ncbi.nlm.nih.gov.
  4. ^ Stylianos Sifniades, Alan B. Levy, "Acetone" in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a01_079.pub3
  5. ^ SIDS Initial Assessment Report for SIAM 13: Hexylene Glycol
  6. ^ MPD at Hampton Research , MPD Product Page
  7. ^ Hexylene Glycol at Sigma Aldrich , Hexylene Glycol Product Page
  8. ^ Hexylene Glycol at Jena Bioscience, Hexylene Glycol Product Page
  9. ^ Chemicalland21.com Hexylene glycol
  10. ^ Kinnunen, T. (1991). "Antibacterial and antifungal properties of propylene glycol, and 1,3-butylene glycol in vitro". Acta Dermato-Venereologica. doi:10.2340/0001555571148150. S2CID 13239472.
  11. ^ R. Rietschel; J. Fowler; A. Fisher Hexylene Glycol. In Fisher's Contact Dermatitis; Holmes, M., Ed.; BC Decker Inc.: Hamilton,Ontario, 2008; pp 290
  12. ^ Rhodia Hexylene glycol GPS Safety Summary. 2012.
  13. ^ Crystallization Techniques: Additives, Enrico Stura, University of Glasgow
  14. ^ Dumetz, A. (2009). "Comparative Effects of Salt, Organic and Polymer Precipitants on Protein Phase Behavior and Implications for Vapor Diffusion". J. Cryst. Growth. 9 (2): 682–691. doi:10.1021/cg700956b.
  15. ^ a b Anand, K (2002). "An overview on 2-methyl-2,4-pentanediol in crystallization and in crystals of biological macromolecules". Acta Crystallogr. 58 (10): 1722–1728. Bibcode:2002AcCrD..58.1722A. doi:10.1107/s0907444902014610. PMC 7161645. PMID 12351894.
  16. ^ Viatcheslav, Berejnov (2006). "Thornea Effects of cryoprotectant concentration and cooling rate on vitrification of aqueous solutions". J. Appl. Crystallogr.
  17. ^ Vera, L (2006). "Strategies for Protein Crystallography". Cryst. Growth Des.
  18. ^ "GreenLube". Allied High Tech. Retrieved 2023-09-23. GreenLube is a medium viscosity hexylene glycol based lubricant used for general metallographic preparation
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