What are the advantages and disadvantages of SMILES, InChIs and InChIKeys?


SMILES (Simplified Molecular Input Line Entry Specification)
A major advantage of the SMILES system is the extensive software support of the algorithm. Many molecule editors allow for the conversion of the two-dimensional structure into the SMILES format. Link Other friendly features of this system are it's simple and compact nature, allowing for it to be relatively human understandable. Link In addition, it can also handle the representation of isotopes and reactions. Link

InChIs (International Chemical Identifier)
This is the first major non-proprietary computerized molecular structure representation algorithm that preserves the uniqueness of a particular compound. It was inspired by the IUPAC compound naming system. LinkHowever, this system presented an issue during searches. Link

InChIKeys
This format which is a hashed version of the InChI system was developed for the purpose of easier searching. Link However, this hashed version of InChI allows for duplicate values. Though the probability of finding a duplicate value is very small. Link


Summary of Article
Investigation on combustion and emissions of DME/gasoline mixtures in a spark-ignition engine
Fuel
Volume 90, Issue 3, March 2011, Pages 1133-1138
Changwei Ji,Chen Liang, Shuofeng Wang
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DOI
[Full Marks JCB]

Introduction
  • There are many chemical and physical properties that make dimethyl ether (DME) quite favorable for combustion in an internal combustion engine.
  • DME is also very environmentally friendly both before and after its combustion.
  • The relatively lower energy output of DME causes a decrease in octane rating of the gasoline it is mixed with.

Experimental setup
  • The apparatus of the experiment, a spark ignition engine that had been fitted with additional injectors for DME, is described in detail.
  • The input parameters, output parameters and variables are prepared for recording by assorted instrumentation.
  • The error in each instrument is noted.

Experimental procedure
  • Engine speed, manifold pressure and fluid temperatures were among some of the values listed at which the experiment was conducted.
  • While running the experiment, the DME content of the mixture was varied.
  • Equations for the DME energy fraction, reactant ratios, and the total energy flow rate are provided.

  • Constants and parameters that are used in the equations that are described in the previous paragraphs are listed with units.
  • Corrections to the spark timing is described.
  • The measurement software and the measurements it made are introduced.

Fuel energy flow rate
  • The decrease in output energy as a function of increasing DME concentration is discussed.
  • It is noted that since the DME is injected in a gaseous phase it will be in competition for the same space that the air usually occupies. (A major influence on the total output)

Brake thermal efficiency
  • A relationship between "brake thermal efficiency" and the "DME energy fraction" is presented.
  • This curve increases, peaks, then decreases, showing that the "brake thermal efficiency can be maximized at a certain reactant ratio.

Combustion
  • The flame development duration and the flame propagation durations are defined.
  • These terms were used in the correction of the spark timing to achieve maximum torque with minimum knocking.

  • The flame development duration decreases as the DME ratio increases.
  • The reasons for this have to do with the premature oxidation of the DME and also with the modified spark timing at high DME ratios.

  • The flame propagation duration is described as a function of the DME ratio.
  • This curve decreases to a minimum, and then rises.
  • It is proposed that this minimum point could be caused by the DME accelerating the gasoline combustion with air.

  • The measurement of the baseline peak cylinder temperature is made by a run with only gasoline.
  • As the DME ratio increases, the peak cylinder temperature decreases, which is consistent with the lower combustion energy of DME.

Cyclic variation
  • Statistical analyses are applied to assess the variation in the mean effective pressure.
  • This demonstrates the effects that flame development and propagation have on the system.

Untreated emissions
  • The hydrocarbon emissions are reported as a function of %DME.
  • The data shows that the increased DME promotes a more complete combustion of hydrocarbons until it reaches a point that it begins to do the opposite.

  • The Nitrogen based emissions decrease as %DME increases. This is caused by the decrease in the air (nitrogen source) in the reactants.

  • The CO output reaches a minimum near the same input ratios as observed at the minimum of flame propagation time.
  • It is hypothesized that this could be due to the lack of time for carbon monoxide to oxidize to form carbon dioxide.

Conclusions
  • In spite of the decrease in input potential energy with the addition of DME, the brake thermal efficiency increases.
  • The addition of DME reduced the operating temperature, reduced the unwanted emissions, and changed the flame characteristics.








Compound: Aspartame
Chemical Property: Melting Point

Source
Value
Source Unit
Common Value
Common Unit
Website
Drug Bank
246 - 247
C
519.65
K
http://www.drugbank.ca/drugs/DB00168
Oxford
249
C
522.15
K
http://msds.chem.ox.ac.uk/AS/aspartame.html
Sigma-Aldrich
248 - 250
C
522.15
K
SUPELCO&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC
Alfa Aesar
243 - 245
?
517.15
K
http://www.alfa.com/en/GP100w.pgm?DSSTK=J61523
Science Lab
248
C
521.15
K
http://www.sciencelab.com/msds.php?msdsId=9922975
CRC Handbook
245
C
518.15
K
http://www.amazon.com/gp/search?index=books&linkCode=qs&keywords=0849305438

[Put in ChemInfo Sheet and I will grade it there JCB]

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