Morpholine

Morpholine is an organic chemical compound having the chemical formula O(CH2CH2)2NH. This heterocycle features both amine and ether functional groups. Because of the amine, morpholine is a base; its conjugate acid is called morpholinium. For example, treating morpholine with hydrochloric acid makes the salt morpholinium chloride. The naming of morpholine is attributed to Ludwig Knorr, who incorrectly believed it to be part of the structure of morphine.[5]

Not to be confused with morphine or morpholino.
Morpholine[1]
numbered skeletal formula of the morpholine molecule
perspective skeletal formula of the morpholine molecule
ball-and-stick model of the morpholine molecule
space-filling model of the morpholine molecule
Names
Preferred IUPAC name
Morpholine
Other names
Diethylenimide oxide
1,4-Oxazinane
Tetrahydro-1,4-oxazine
Diethylene imidoxide
Diethylene oximide
Tetrahydro-p-oxazine
Identifiers
3D model (JSmol)
102549
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.003.469
EC Number
  • 203-815-1
1803
KEGG
RTECS number
  • QD6475000
UNII
UN number 2054
Properties
C4H9NO
Molar mass 87.122 g·mol−1
Appearance Colorless liquid
Odor Weak ammonia-like or fish-like[2]
Density 1.007 g/cm3
Melting point −5 °C (23 °F; 268 K)
Boiling point 129 °C (264 °F; 402 K)
miscible
Vapor pressure 6 mmHg (20 °C)[2]
Acidity (pKa) 8.36[3] (of conjugate acid)
-55.0·10−6 cm3/mol
Hazards
Main hazards Flammable, Corrosive
Safety data sheet hazard.com
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H226, H302, H312, H314, H332
P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P280, P301+312, P301+330+331, P302+352, P303+361+353, P304+312, P304+340, P305+351+338, P310, P312, P321, P322, P330, P363
NFPA 704 (fire diamond)
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
3
0
Flash point 31 °C (88 °F; 304 K)
275 °C (527 °F; 548 K)
Explosive limits 1.4%–11.2%[2]
Lethal dose or concentration (LD, LC):
1220 mg/kg (mammal, oral)
525 mg/kg (mouse, oral)
1050 mg/kg (rat, oral)[4]
365 ppm (mouse, 2 hr)[4]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 20 ppm (70 mg/m3) [skin][2]
REL (Recommended)
 TWA 20 ppm (70 mg/m3) ST 30 ppm (105 mg/m3) [skin][2]
IDLH (Immediate danger)
 1400 ppm[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Production

Morpholine is often produced industrially by the dehydration of diethanolamine with sulfuric acid:[6]

Uses

Industrial applications

Morpholine is a common additive, in parts per million concentrations, for pH adjustment in both fossil fuel and nuclear power plant steam systems. Morpholine is used because its volatility is about the same as water, so once it is added to the water, its concentration becomes distributed rather evenly in both the water and steam phases. Its pH-adjusting qualities then become distributed throughout the steam plant to provide corrosion protection. Morpholine is often used in conjunction with low concentrations of hydrazine or ammonia to provide a comprehensive all-volatile treatment chemistry for corrosion protection for the steam systems of such plants. Morpholine decomposes reasonably slowly in the absence of oxygen at the high temperatures and pressures in these steam systems.

Organic synthesis

Morpholine undergoes most chemical reactions typical for other secondary amines, though the presence of the ether oxygen withdraws electron density from the nitrogen, rendering it less nucleophilic (and less basic) than structurally similar secondary amines such as piperidine. For this reason, it forms a stable chloramine.[7]

It is commonly used to generate enamines.[8]

Morpholine is widely used in organic synthesis. For example, it is a building block in the preparation of the antibiotic linezolid, the anticancer agent gefitinib (Iressa) and the analgesic dextromoramide.

In research and in industry, the low cost and polarity of morpholine lead to its common use as a solvent for chemical reactions.

Agriculture

As a fruit coating

Morpholine is used as a chemical emulsifier in the process of waxing fruit. Naturally, fruits make waxes to protect against insects and fungal contamination, but this can be lost as the fruit is cleaned. A small amount of new wax is applied to replace it. Morpholine is used as an emulsifier and solubility aid for shellac, which is used as a wax for fruit coating.[9] The European Union has forbidden the use of morpholine in fruit coating.[10][11]

As a component in fungicides

Morpholine derivatives used as agricultural fungicides in cereals are known as ergosterol biosynthesis inhibitors.

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See also

References
  1. National Institute for Occupational Safety and Health (2000). "Morpholine". International Chemical Safety Cards. Retrieved 5 November 2005.
  2. NIOSH Pocket Guide to Chemical Hazards. "#0437". National Institute for Occupational Safety and Health (NIOSH).
  3. Hall, H. K. (1957). "Correlation of the Base Strengths of Amines1". J. Am. Chem. Soc. 79 (20): 5441–5444. doi:10.1021/ja01577a030.
  4. "Morpholine". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  5. F. Silversmith, Ernest; Nickon, Alex (2013-10-22). Organic Chemistry : Modern Coined Terms and Their Origins. Elsevier Science. p. 313. ISBN 978-1483145235.
  6. Weissermel, Klaus; Arpe, Hans-Jürgen; Lindley, Charlet R.; Hawkins, Stephen (2003). "Chapter 7. Oxidation Products of Ethylene". Industrial Organic Chemistry. Wiley-VCH. pp. 159–161. ISBN 3-527-30578-5.
  7. Lindsay Smith, J. R.; McKeer, L. C.; Taylor, J. M. (1993). "4-Chlorination of Electron-Rich Benzenoid Compounds: 2,4-Dichloromethoxybenzene". Organic Syntheses.; Collective Volume, 8, p. 167
  8. Noyori, R.; Yokoyama, K.; Hayakawa, Y. (1988). "Cyclopentenones from α,α′-Dibromoketones and Enamines: 2,5-Dimethyl-3-Phenyl-2-Cyclopenten-1-one". Organic Syntheses.; Collective Volume, 6, p. 520
  9. McGuire, Raymond G.; Dimitroglou, Dimitrios A. (1999). "Evaluation of Shellac and Sucrose Ester Fruit Coating Formulations that Support Biological Control of Post-harvest Grapefruit Decay". Bio-control Science and Technology. 9 (1): 53–65. doi:10.1080/09583159929901.
  10. "Morpholine". Scientific Analysis Laboratories Ltd. Archived from the original on 2012-04-26.
  11. "Morpholine Issues in the United Kingdom". Northwest Horticultural Council. September 28, 2010. Archived from the original on April 26, 2012.
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