MM-Wave Rotational Spectrum of Methyl Nitrate

Jessica Thomas, Ivan Medvedev, Department of Physics, Wright State University

David DolsonDepartment of Chemistry, Wright State University

• Chemical related to metabolism

• With diabetes this chemical has been known to be on the order of parts per trillion.

• Also, it is known to be expressed in breath in children with type 1 diabetes.

• Likely, oxidative stress on individuals during hyperglycemia in type 1 diabetics causes methyl nitrate production.

• Could be an indicator used for air quality monitoring

• Possesses explosive qualities

• Could be a molecule of interest in interstellar medium

OUR INTEREST IN METHYL NITRATE

http://commons.wikimedia.org/wiki/File:Methyl_nitrate_3D_ball.png

The synthesis of this chemical was done by scaling down and following the procedures published in Organic Syntheses. Our experiment was done to yield roughly 3-4 ml of MeONO2.

THE SYNTHESIS

Drying Setup

Glass Wool

CaCl2

3-4mL MeONO2

•Nitration of methanol by a mixture of sulfuric and nitric acid.

•Sulfuric acid is used as a catalyst and an absorber of water

•The product was dried to remove any excess water

http://commons.wikimedia.org/wiki/File:Methyl_nitrate_3D_ball.png

METHYL NITRATE, THE MOLECULE

Molecular Formula CH3NO3

Molar Mass 77.04 g/mol

Density 1.203 g/cm3

Melting point -82.3C

Dipole moment μa = 3.1 Dμb = .25 D

• Colorless volatile liquid

• Ignited, it burns with a gray-blue flame

• Toxic when inhaled

• Difficult to store for extended periods of time

PREVIOUS RESEARCH

Dixon, W., & Wilson JR, E. B. (1961, July 1). Microwave Spectrum of Methyl Nitrate. The Journal of Chemical Physics, 35, 191-198.

Parameter

A / MHz 11795.06

B / MHz 4707.52

C / MHz 3438.29

Ia / amu A2 42.8596

Ib/ amu A2 107.388

Ic/ amu A2 147.030

Ia+ Ib- Ic 3.218

ҡ -0.696239

This paper also discusses briefly the excited state of methyl nitrate.

SUBMILLIMETER ROTATIONAL SPECTRA OF METHYL NITRATE, Drouin, Brian J.; Zhang, Xu; Ellison, G. Barney, 2008, Columbus (400-440 GHz)

IF

VDI

Tran

smitt

er

VDI

Rece

iver

Absorption Cell: length - 2 m ,volume - 14 L

x24

SteppingSynthesizer

LO

Sidebandfilter

Computer

IF detectorLock in

SweepingSynthesizer

Gas Inlet

Absorption CellCustom Built Microwave

Synthesizer

Continuous Wave THz Spectrometer

Microwave Synthesizer

Custom Built

Diode Multipliers Virginia Diodes

Absorption Cell 2 m long by 4in wide (14 L)

OUR SYSTEM

THE SPECTRUM

•prolate asymmetric top with the moments of inertia along the three principle axes falling into the order IaIbIc.

•For asymmetric tops the allowed transitions all obey selection rules ∆J = 0, ±1 and the components of dipole moments dictate the transitions between Ka and Kc.

B

CA

•a-type transition has the selection rules ∆ Ka = 0(±2,±4) and ∆ Kc = ±1(±3,±5)

•b-type transition has the selection rules ∆ Ka = 1(±3,...) and ∆ Kc = ±1(±3,…)

Ground State

1st Excited State

GROUND STATE

265 lines assigned with J numbers ranging from 24 to 38

Parameter Current Valuea Previous ValueA / MHz 11795.12844(259) 11795.06

B / MHz 4707.57017( 78) 4707.52

C / MHz 3438.24379( 77) 3438.29

ΔJ / kHz 0.974760(295)  

ΔJK / kHz 4.32862(109)  

ΔK / kHz 4.4918(172)  

δJ / kHz 0.249434(199)  

δK / kHz 2.7136( 43)  

Avg. / kHz .561  rms /kHz 56.967  

NUMERICS

Parameter Old Values Current ValueA / MHz 11795.06 11795.12844(259)B / MHz 4707.52 4707.57017( 78))C / MHz 3438.29 3438.24379( 77)

Ia / amu A2 42.8596 42.85930438Ib/ amu A2 107.388 107.386822Ic/ amu A2 147.030 147.0317496

Ia+ Ib- Ic 3.218 3.214376799ҡ -0.696239 -0.696220199

1ST EXCITED STATE

1ST EXCITED STATE

Perturbed lines from likely a combination of the v=1 methyl torsion and the v=1 NO2 torsion.

Upper state: 30 6 25Lower state: 29 6 24a,q,R,30,-1

Upper state: 31 5 27Lower state: 30 5 26a,q,R,31,-1

Upper state: 28 8 20Lower state: 27 8 19a,q,R,28,0

Upper state: 31 4 27Lower state: 30 4 26a,q,R,31,0

Parameters Tentative Values

A / MHz 11760.80302(277)

B / MHz 4704.80082(147)

C / MHz 3442.22668(130)

AVG/ MHz -0.002452

RMS/MHz 1.048496

1ST EXCITED STATE

Upper state: 29 7 22Lower state: 28 7 21A,q,R,29,0

CONCLUSION AND STEPS FORWARD

This experiment assigned the ground state and offered a rough estimate of the assignment of first vibrational state between 210 -270. By doin so we were able to refined the rotational constants that were furnished by previous the microwave study of this molecule.

•Refine line lists•Work towards the assignment of the excited state•Extend assignment beyond 270 GHz

Goals: