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Dalapon

Names
IUPAC name 2,2-dichloropropionic acid
Systematic IUPAC name 2,2-dichloropropionic acid
Other names 2,2-Dichloropropionic acid, 2,2-Dichloropropanoic acid, Kenapon, Liropon, Proprop, Alatex, Unipon, Sys-Omnidel, D-Granulat
Identifiers
CAS Number	75-99-0 Y
3D model ( JSmol )	Interactive image
ChemSpider	6178
EC Number	200-923-0
PubChem CID	87568185
RTECS number	UF0690000
UNII	VO6PY8ZMRW Y
InChI InChI=1S/C3H4Cl2O2/c1-3(4,5)2(6)7/h1H3,(H,6,7)
SMILES CC(C(=O)O)(Cl)Cl
Properties
Chemical formula	C3H4Cl2O2
Molar mass	130.98 g/mol
Appearance	Colorless liquid with a strong, sharp odor.
Density	1.361 g/cm 3
Melting point	98°C
Boiling point	202°C
Solubility in water	800g/L of water at 25 degrees Celsius
Vapor pressure	5.1 mm Hg at 71°C
Acidity (pKa)	1.53
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Causes burning and irritation in eyes and on skin. If inhaled causes nose, throat and lung irritation. Also causes dizziness, weakness, headaches, vomiting, and nausea.
Flash point	>110
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Dalapon

Properties

Dalapon, 2,2-dichloropropionic acid, is an acid that is most typically formulated with sodium or magnesium salts. Dalapon in its purest form is found as a clear colorless liquid. When dalapon is mixed with the magnesium and sodium salts, a sodium magnesium salt is formed. As sodium-magnesium salts, it is a white to off-white powder. Dalapon is a substance that will readily take up water or other various types of moisture. Overall Dalapon is known to be nonflammable however under certain conditions it can pose a slight flammability hazard. Dalapon can undergo hydrolysis from temperatures ranging from 25 degrees Celsius to 50 degrees Celsius at which the temperature is optimal for rapid hydrolysis. When this molecule is exposed to oxidizers, incidence of flammability increases. The acidic pH of this molecule is 1.32 and has a melting point of 166.32 degrees Celsius. Dalapon is also highly soluble in ethanol. It has a molecular formula of C3H4O2Cl2. It also has the property of high mobility in water.

Occurrences

Herbicides have played a vital role in crop production for over 60 years in Western Canada. Production of herbicides was quite prominent in the past, but with the emergence of herbicide resistant weeds, the efficiency of these chemicals have significantly deteriorated. This has stimulated the market for the production of new alternatives for efficient weed-management systems for farmers and their crops. It once was an effective method to substantially increase crop yields and their quality. Dalapon, registered in 1955, was a significant but now obsolete herbicide.

Uses

Dalapon is used to control the growth of grass in many different types of plants such as trees and cotton plants. Dalapon is released to the environment for the inhibition of annual and perennial grasses.^[1] If it is released into the soil, microbial degradation can occur. It has also found an effective role in various non-crop applications such as lawns, drainage ditches, along railroad tracks, and in industrial scene as well.

Production

Dalapon domestic production began in 1982. In 1984, it became readily useable in California most notable for non-food use.

Dalapon is not a listed chemical in the Toxics Release Inventory, data on releases during its manufacture and handling are not available.The preparation of dalapon is a simple process. Methods report preparing this compound using the isotopic exchange at 120 °C. When the isotopic exchange is in acetone at the exchange medium under the vacuum, the compound is labeled with sodium chloride at 140 °C and evacuated and sealed in a reaction tube without any other exchange medium. When dalapon is a liquid and with a boiling point of 185-192 °C, it can serve as an ideal isotopic exchange medium. When the labelled dalapon was obtain in high yield (90%) after vacuum distillation at 65-70 °C. The radiochemical yield varied between 60-70%.^[2]

Formation

The first step of the formation of 2,2-dichloropropionic acid is the substitution of the methyl group. The chlorine acts as a nucleophile and attacks that carbon and substituting the methyl group. In the next stem, Cl₂ does the same reaction to the other methyl group on the carbon but this time the -OH₂⁺ is also deprotonated. In the last step, the -OH of the carboxylic acid deprotenates the oxygen of Na-OH, breaking the O-H bond and those electrons are donated to the oxygen. The newly negatively charged oxygen acts as a nucleophile and attacks the carbonyl carbon, causing the double bond of the C=O to break and the pi electrons are donated to the carbonyl oxygen. That oxygen now has a negative charge and uses its lone pair to reform the double bond and kick of the newly formed good leaving group -OH₂⁺ forming Dalapon or 2,2-dichloropropionic acid.

Safety

Storage of Dalapon

Dalapon is stable under normal temperature and pressure but poses a hazardous risk of fire and explosion in the presence of strong oxiders. Solutions of sodium-dalapon are corrosive to certain elements such as iron. Therefore properly handing, treatment, and storage of this chemical is strongly advised in all environments.

Research

In an experiment, researchers used dalapon as the sole carbon source for 4 different bacterial strains. They then analyzed the rDNA from the bacteria in order to complete a study of the genus of the bacteria. Their goal of this experimental study was to pinpoint bacteria that had the ability to use Dalapon as their only source of carbon to see if the bacterial strains could use, as well as degrade the dalapon molecule at a high rate.^[3] They found that four out of the ten took a short time to form colonies that were observable. They used this information to infer that dalapon was efficiently used as the only carbon source and from this information they continued on to analyze the growth profile of each of the colonies that were able to grow and produce colonies beyond the initial phases. With this information they then were able to establish the bacterial lineage that these particular colonies stemmed from. They also found that at too high of concentrations, dalapon is toxic and therefore the bacteria could not obtain growth at these high concentrations. They concluded that dalapon as an example of a dehalogenase gene are well distributed and conserved across the wide spectrum of the microbial genera. Also, the high growth rate of one of the colonies indicated that this particular bacterial strain was able to utilize residual dalapon that was in the soil or in natural environment.

Experimental Design with Dalapon

Dalapon has been extensively used in research to finding a particular method to aid in controlling the growth of annual grasses in crop production. Specifically, dalapon has been tested to control the growth of grass in sugar beets.^[4] Research has been conducted to find an alternative to pre-emergence sprays which have proven to have a negative effect on the yield of their product. This is where Sodium Dalapon has been implemented. However, the success of this chemical depends on the application of water in order for the toxic herbicide to properly reach the roots within the soil. Dalapon has proven to absorb through leaves and roots. The first application of Dalapon took place in the summer of 1952 to control the growth of watergrass. To validate the results obtained, the same experiment was conducted the following year with four distinct goals: to determine the effect of dalapon on the yield of beets, the optimum volume rate, the relationship of growth stage grasses on dosage, and the effect on environmental conditions. Upon conclusion of the experiment, the results were inconclusive to say the least. It was determined that more research is necessary before dalapon can be used to effectively control the growth of sugar beets. It was further noted in 1954 that dalapon will be recommended for only non-crop grass control.

Toxicity

Dalapon has proven to have acute toxicity effects on humans.^[5] Such symptoms of high acute exposure include loss of appetite, slowed heartbeat, skin irritation, and eye irritation. There is insufficient evidence to prove that high exposure to Dalapon does in fact cause cancer in humans. The half-life of Dalapon is about 1.5–3 days in human blood. This halogenated compound also degrade the environment.^[6]

References