Clam compound

A number of bridged crown ethers have been prepared. Although the Simmons-Park in-out bicyclic amines (see Sect. 1.3.3) are the prototype, Lehn s cryptands (see Chap. 8) are probably better known. Intermediates between the cryptands (which Pedersen referred to as lanterns ) and the simple monoazacrowns are monoazacrowns bridged by a single hydrocarbon strand. Pedersen reports the synthesis of such a structure (see 7, below) which he referred to as a clam compound for the obvious reason . Although Pedersen appears not to have explored the binding properties of his clam in any detail, he did attempt to complex Na and Cs ions. A 0.0001 molar solution of the clam compound is prepared in ethanol. The metal ions Na and Cs are added to the clam-ethanol solutions as salts. Ultraviolet spectra of these solutions indicate that a small amount of the Na is complexed by the clam compound but none of the Cs . 

Although the clam structures are of interest as ammonium ion binders, they are by no means the only azacrown compounds of interest in this application. Sutherland and coworkers have examined a number of azacrowns as primary ammonium ion bind-ers - . In addition, Metcalfe and Stoddart have utilized bis-azacrowns to bind secondary ammonium cations. 

Bangor Naval Submarine Base, on the Hood Canal in the State of Washington, provides fine recreational facilities for service people stationed there, as well as for civilian employees. A proposal to divert runoff from munitions-contaminated areas towards the recreational fishing pond, Cattail Lake, led to a decision to identify hazard levels for the compounds of interest. In addition to trout, there was concern over contamination of bivalves, such as oysters, cockles, and clams, at the pond s outlet to Hood Canal. Bioconcentration factors (BCFs), assumed applicable for both fish and bivalves, were developed for three compounds (Table III). BCFs, together with Uj. values and worst-case levels of fish or bivalve consumption (0.4 kg/day) provided PPLVs for the pond water, according to the equation... 

Wong and coworkers118 analyzed fish and other environmental samples (clam, macrophytes, sediments and waters) from areas upstream and downstream from alkyllead manufacturing sites beside the St. Lawrence and St. Clair Rivers, Ontario, and found a clear indication of elevated alkyllead levels in samples near the industries. Most species of fish contained alkyllead compounds with tetraethyllead and triethyllead as the predominant forms. Most fish from the contaminated areas contained 70% or more of the total lead as alkyllead. Average alkyllead levels varied from year to year but declined steadily after 1981. For example, the mean value of alkyllead in carp from the St. Lawrence River decreased from 4207 H g kg-1 in 1981 to 2000 H g kg-1 in 1982 and to 49 Xg kg 1 in... 

Exposure to heptachlor and heptachlor epoxide most commonly occurs when you eat contaminated food. Contaminated foods might include fish, shellfish (e.g., clams), dairy products, meat, and poultry. Children and toddlers drink large amounts of milk and may have greater exposure if the milk is contaminated with heptachlor or heptachlor epoxide. Infants can be exposed to these compounds from consumption of contaminated maternal or cow s milk. Exposure can also occur when you drink water, breathe air, or touch contaminated soil at hazardous waste sites that contain heptachlor or heptachlor epoxide. People whose homes have been treated with heptachlor to kill termites can be exposed by breathing heptachlor in the air. After heptachlor is changed to heptachlor epoxide in the soil, it can get into the air. People who breathe this air will be exposed to heptachlor epoxide. 

Heptachlor and heptachlor epoxide have been detected in several aquatic species. Heptachlor was measured in shrimp collected from the Calcasieu River/Lake Complex in Louisiana at concentrations ranging from 10 to 750 ppb (Murray and Beck 1990). A survey of organic compound concentrations in whole body tissues of the Asiatic clam Corbicula manilensis was conducted on the Apalachicola River in northwest Florida in 1979-1980 as part of the Apalachicola River Quality Assessment. Heptachlor epoxide was detected in the whole body tissue of the clam at concentrations ranging from <0.1 to 0.6 ppb, with a median concentration of 0.3 ppb (Elder and Mattraw 1984). 

Carbon is, without a doubt, one of the most important elements on Earth. It is the major element found in over one million organic compounds and is the minor component in minerals such as carbonates of magnesium and calcium (e.g., limestone, marble, and dolomite), coral, and shells of oysters and clams. 

Humans may be programmed to be more sensitive to natural food contaminants. For instance, (-)geosmin (rrans-l,10-dimethyl-rran5-9-decalol) occurs in earth, natural surface water, and in foods in contact with soil or water, such as beets, clams, or fish. Geosmin is a microbial, fungal, or algal metabolite. It is a water pollutant and off-flavor compound. The naturally occurring (-)enantiomer has a threshold 11 times lower than the (-I-) enantiomer (Polak and Provasi, 1992). 

In addition to these passive processes shellfish have been shown to actively modify the saxitoxins. Shimizu has shown (40) that scallops can remove both the N-l-hydroxyl and 11-hydroxysulfate groups from the saxitoxins. Sullivan has shown ( ) that enzymes in littleneck clams can remove the sulfamate or carbamate side chain, yielding the decarbamoyl toxins. This activity was not detected in either mussels or butter clams. With both sorts of modification the products are compounds that have higher potency and are likely to be bound in shellfish more strongly. 

Figure 10.7 Schematic illustration of uptake and depuration of chemicals by a benthic organism, a clam dwelling near the sediment-water interface. iw is the truly dis-solved compound in the water column, ipom is the compound asso-ciated with the sediment organic matter, ipw is the compound dis-solved in the sediment porewater.

Calcium carbonate (CaCOj) is the starting point for most calcium compounds — and for oilier chemicals as well. It is found in nature in cliffs and mountain ranges in the form of chalk and limestone and marble. And it makes up the shells of clams and mussels and billions of tiny sea creatures. 

Radiation Biochemistry of Flavor and Odor. Some 17 carbonyl compounds have been isolated in irradiated fish, and 12 have been identified. Nonirradiated clams show an increase in carbonyls during storage. Following irradiation at 450 krads the concentration of carbonyls increases sharply. The use of cryogenic temperatures significantly lowers the production of carbonyls. (2). 

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