Amino Alcohols

After reviewing the work of Azrak and Angell (Azrak and Angell, 1973), which suggested that amino alcohols may covalently bond more readily with silicates than regular alcohols, it was only logical to investigate amino alcohols in addition

Table 2. Summary of the interactions of various organic compounds with sodium silicate.

Class of organic molecule Notes

Amino acids (AA) Mechanism: Catalysis. Entombment possible in trace amounts; low levels of organics detected in some cases. Biological AA Gel formation and appearance: Immediate formation of rubbery or hard whitis

Meteoritic AA (Sarcosine a h opaque gels. Gels are not water-soluble. Dried gels consist of nd 5-aminovaleric acid) small white chunks and powder.

Sol-gel-sol transformation: Some transformations were seen. Gel formation and appearance: Sarcosine behaved similarly to the biological A.A

. 5-Aminovaleric acid did not result in immediate gel formation. Gel isolated from 5-aminovaleric acid was water-soluble. Sol-gel-sol transformation: Some transformations were seen with sarcosine.

Maillard mixtures Mechanism: Catalysis. Entombment possible in trace amounts; low levels of organics detected in some cases.

Gel formation and appearance: Rubbery gels quickly form, often within a minute or less. Gels are originally whitish but darken to orange and brown within days. Dried gels consist of white chunks and powder.

Sol-gel-sol transformation: Major transformations were seen. Maillard-metal complexes Mechanism: Catalysis. No organics detected in the IR spectra.

Gel formation and appearance: Soft gels quickly form, often within seconds, but may take up to 30 minutes to form. Gels are brownish. Dried gels from Fe-containing complexes were gray in color. All other metals resulted in whitish dried gels. Sol-gel-sol transformation: Major transformations were seen. Other: The gels from Fe-containing complexes were the only ones in our laboratory that kept a distinct color after being dried. Sugars and sugar alcohols Mechanism: Catalysis. No organics detected in the IR spectra to suggest otherwise. C-13 and Si-29 NMR studies suggest covalent bond formation occurs leading to the formation of water-soluble organo-silicates.

Gel formation and appearance: Soft, transparent gels form slowly and darken over hours and days. Gels partially water-soluble. Dried gels consist of small white chunks. Sol-gel-sol transformation: Some transformations were seen. Alcohols Mechanism: Catalysis. No organics were detected in the IR spectra.

Gel formation and appearance: Gel appearance depended upon the volume of alcohol added. Initially a low-viscosity gel formed. Firm, rubbery gels could be formed upon adding an additional amount of alcohol. Gels are partially water-soluble. Dried gels were opaque and rubbery. These gels lost their integrity upon standing and several chunks would fuse together to form a single mass. Sol-gel-sol transformation: Unique transformations were seen related to viscosity trends and water-solubility. Other: The volume-dependency and appearance of these gels was unique. Small alcohols with more compact structures are more efficient in the silica polymerization.

(continued)

Table 2. (continued)

Class of organic molecule

Notes

Amino alcohols

Acid halides

Other key biomolecules

Urea AMP

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