|Chemical Abstract Number (CAS #)||
|Synonyms||Molinate||1H-Azepine-1-carbothioic acid, hexahydro-, S-ethyl ester||S-Ethyl hexahydro-1H-azepine-1-carbothioate||Jalan||Yalan
||EPA Method 634|
Link to the National Library of Medicine's Hazardous Substances
Database for more details
on this compound.
|Use|| SELECTIVE HERBICIDE
Registered for use on rice for the control of watergrass (Echinochloa species) and other weeds.
MOLINATE IS TOXIC TO GERMINATING BROAD-LEAVED & GRASSY WEEDS & IS
PARTICULARLY USEFUL FOR CONTROL OF ECHINOCHLOA SPECIES IN RICE @ 2-4
|Apparent Color|| CLEAR LIQUID ; Amber liquid
|Boiling Point|| 202 DEG C @ 10 MM HG
|Molecular Weight|| 187.33
|Density|| 1.5156 @ 30 DEG C/D
|Sensitivity Data|| Irritating to skin and eyes .
|Environmental Impact|| Molinate is released directly to the environment through its use and application as an
agricultural herbicide . If released to soil, microbial degradation will be the major environmental
degradation process. The half-life of molinate in soil is reported to be about 3 weeks; half-life of
applications to flooded rice fields are reported to range from about 1 to 6 days. Field studies have
shown that volatilization can be the dominant removal process for molinate applications to soil
and flooded rice field surfaces; molinate is readily lost from soil by volatilization at the time of
application when the herbicide is not incorporated into the soil immediately. Molinate will leach
readily. If released to water, molinate will degrade through biodegradation and photodegradation
(via sunlight formed hydroxyl radicals). Anaerobic conditions retard microbial degradation.
Volatilization from warm, shallow waters of flooded rice fields (or similar conditions) can be a
major removal mechanism; however, volatilization of dissolved molinate from deeper rivers or
lakes is expected to be slow. If released to the atmosphere, molinate will exist primarily in the
vapor phase; vapor phase molinate degrades readily by reaction with photochemically produced
hydroxyl radicals (estimated half-life of 12.7 hours). Physical removal from the atmosphere may
occur through wet and dry deposition. Occupational exposure to molinate occurs through dermal
contact and inhalation of dust.
|Environmental Fate|| Ordram was applied in granular form to flooded rice paddy. The half-life of Ordram was
less than 100 hr. No significant residues were present in the water after 192 hr.
In a rice field, Ordram was half gone in 3 days. About 80% of the Ordram was lost by
Field studies conducted under flooded rice cultivation indicated that molinate had a half-life of 74
to 118 hr in intermittent flow plots and 37 to 71 hr in continuous flow plots. The half-life was not
dependent on application rate.
TERRESTRIAL FATE: Biodegradation is the major degradation process for molinate in soil .
Degradation studies have shown that molinate will degrade more rapidly in non-sterile soil than in
sterile soil . Degradation under anaerobic soil conditions is reported to be slower than under
aerobic conditions . Field studies have shown that volatilization can be the dominant removal
process for molinate applications to soil and flooded rice field surfaces(4-5). Molinate is readily
lost from soil by volatilization at the time of application when the herbicide is not incorporated
into the soil immediately . It is adsorbed by dry soil, but is readily removed by leaching as
predicted by Koc values of 80-190(6-7). The half-life in most loam soils (at 21-27 deg C) is
approximately 3 weeks ; the US Dept of Agric's Pesticide Properties Database lists a soil
half-life of 21 days(7). Half-life of applications to flooded rice fields are reported to range from
about 1 to 6 days(3,4,9).
AQUATIC FATE: Molinate can degrade in water through biodegradation and
photooxidation . Molinate has been shown to undergo a photo-sensitized degradation (via
reaction with photochemically formed species such as hydroxyl radicals) in natural water(2-3);
photodegradation rates will depend upon sunlight intensity and availability of sensitizing agents
such as humic materials, amino acids, etc. Anaerobic conditions retard microbial
degradation in aqueous media ; therefore, persistence is expected to increase in anaerobic
conditions with no sunlight exposure.
AQUATIC FATE: Volatilization from warm, shallow waters of flooded rice fields (or similar
conditions) can be a major removal mechanism(1-2); however, volatilization of dissolved molinate
from deeper rivers or lakes is expected to be slow based upon measured Henry's Law
constants(3-4,SRC). Adsorption to sediment will have minor importance based upon measured
Koc values of 80-89(5,SRC). The half-life of molinate in natural waters collected from rice
paddies or rivers fed by rice paddy runoff ranged from 0.6 to 6.6 days(6).
ATMOSPHERIC FATE: Based upon a vapor pressure of 5.6X10-3 mm Hg at 25 deg C ,
molinate will exist primarily in the vapor phase in the ambient atmosphere(2,SRC). It will degrade
readily in the vapor phase by reaction with photochemically produced hydroxyl radicals with an
estimated half-life of 12.7 hr(3,SRC). Physical removal of molinate aerosols (released via spray
applications of molinate herbicides) and particulates by wet (rainfall, etc) and dry deposition
(settling) can also occur.
|Drinking Water Impact|| DRINKING WATER: Tap water samples collected near the Texas Agricultural
Experiment Station near Beaumont, TX in July 1977 contained molinate concns of approximately
33 ppm .
SURFACE WATER: Monitoring of seven Japanese rivers flowing into Lake Biwa in 1988 and