Unsaturation, effects

John, G., Jung, J.-H., Masuda, M. and Shimizu, T. (2004) Unsaturation effect on gelation behavior of aryl glycolipids. Langmuir, 20 (6), 2060-2065. 

The chain unsaturation effect was also studied for dimethylaminopropane (DMA) cationic lipids with 0-3 double bonds per chain [59]. The authors used a series of four lipids of the same alkyl chain length (diCl8) modified with a systematic addition of double bonds, from 0 to 3 per chain distearoyl (DSDMA), dioleoyl (DODMA, dilinoleyl (DLenDMA), and dilinolenoyl (DLinDMA). It was... 

Reagents which effect epoxidation of the enol ether unsaturation effect a-hydroxylation comparable to the peracid approach. Thus a combination of molybdenum hexacarbonyl and r-butyl hydroperoxide converts the substrates to a-silyloxy derivatives. The peroxide generate in situ from benzonitrile, potassium carbonate and hydrogen peroxide can also perform the oxidation. Molybdenum-peroxy complexes, including MoOPH, could presumably also effect this transformation. Lastly, dimethyldioxirane has been used to epoxidize alkenes and it is likely that application of this useful, debris free, organic peroxide to these reactions will soon emerge. 

Beckett and his co-workers (B14) examined the hydrolysis by purified horse serum cholinesterase of a number of analogs of butyrylcholine. The introduction of an a-methyl group into the choline moiety of the butyryl ester was found to decrease the rate of enzymic hydrolysis only slightly, whereas a drastic reduction was found for d-methyl substitution. The substitution of various functional groups into the butyryl moiety of butyrylcholine modified the affinity of the substrate for the enzyme. These results are summarized in Table 3. Since values can be assumed to be inversely proportional to affinity values, the results shown in this table indicate that j8-hydroxyl substitution increases the affinity of the substrate for the enzyme, and a,/3-unsaturation effects even greater affinity. Acetoacetylcholine has a greater affinity for the enzyme surface... 

Javitt DC (2006) Is the glycine site half saturated or half unsaturated Effects of glutama-tergic drugs in schizophrenia patients. Curr Opin Psychiatry 19 151-157... 

Small solvent effects (A) of water on certain proton-transfer equilibria I. Unsaturation effects in the aliphatic series -h (n-Pr)3N = (n-Pr)3NH + B... 

Forbes M D E 1993 The effect of localized unsaturation on the scalar exchange coupling in flexible biradicals J. Phys. Chem. 97 3390-5... 

The meta directing groups include those in which the atom directly attached to the aromatic nucleus is either positively charged or strongly unsaturated. These are, in order of decreasing effectiveness —... 

In unsaturated molecules electronic effects can be transmitted by mesomerism as well as by inductive effects. As with the latter, the mesomeric properties of a group are described by reference to hydrogen. Groups which release electrons to the unsaturated residue of the molecule are said to exert a +Af effect, whereas groups which attract electrons are said to exert a —Af effect. In aromatic structures the important feature of an M-substituent is that it influences the 0- and p-positions selectively. 

Triethylammonium formate is another reducing agent for q, /3-unsaturated carbonyl compounds. Pd on carbon is better catalyst than Pd-phosphine complex, and citral (49) is reduced to citronellal (50) smoothly[55]. However, the trisubstituted butenolide 60 is reduced to the saturated lactone with potassium formate using Pd(OAc)2. Triethylammonium formate is not effective. Enones are also reduced with potassium formate[56]. Sodium hypophosphite (61) is used for the reduction of double bonds catalyzed by Pd on charcoal[57]. 

Conjugation of the newly formed double bond with the carbonyl group stabilizes the a p unsaturated aldehyde provides the driving force for the dehydration and controls Its regioselectivity Dehydration can be effected by heating the aldol with acid or base Normally if the a p unsaturated aldehyde is the desired product all that is done is to carry out the base catalyzed aldol addition reaction at elevated temperature Under these conditions once the aldol addition product is formed it rapidly loses water to form the a p unsaturated aldehyde... 

Aldol condensation offers an effective route to a p unsaturated aldehydes and ketones These compounds have some interesting properties that result from conjugation of the carbon-carbon double bond with the carbonyl group As shown m Figure 18 6 the rr systems of the carbon-carbon and carbon-oxygen double bonds overlap to form an extended rr system that permits increased electron delocalization... 

The intermediate m hydrogenation formed by reaction of the unsaturated ester with the hydrogenated surface of the metal catalyst not only can proceed to the saturated fatty acid ester but also can dissociate to the original ester having a cis double bond or to its trans stereoisomer Unlike polyunsaturated vegetable oils which tend to reduce serum cholesterol levels the trans fats produced by partial hydrogenation have cholesterol raising effects similar to those of saturated fats... 

This mode of termination produces a negligible effect on the molecular weight of the reacting species, but it does produce a terminal unsaturation in one of the dead polymer molecules. Each polymer molecule contains one initiator fragment when termination occurs by disproportionation. 

Residual monomers in the latex are avoided either by effectively reacting the monomers to polymer or by physical or chemical removal. The use of tert-huty peroxypivalate as a second initiator toward the end of the polymeri2ation or the use of mixed initiator systems of K2S20g and tert-huty peroxyben2oate (56) effectively increases final conversion and decreases residual monomer levels. Spray devolatili2ation of hot latex under reduced pressure has been claimed to be effective (56). Residual acrylonitrile also can be reduced by postreaction with a number of agents such as monoamines (57) and dialkylamines (58), ammonium—alkali metal sulfites (59), unsaturated fatty acids or their glycerides (60,61), their aldehydes, esters of olefinic alcohols, cyanuric acid (62,63), andmyrcene (64). 

There is a significant difference in the toxicological effects of saturated and unsaturated afiphatic aldehydes. As can be seen in Table 6, the presence of the double bond considerably enhances toxicity. The precautions for handling reactive unsaturated aldehydes such as acrolein, methacrolein [78-85-3] and crotonaldehyde should be the same as those for handling other highly active eye and pulmonary irritants, as, for example, phosgene. 

The state of knowledge in the early 1990s of the effects of fat on health lacks clarity and general agreement. There is great support for the thesis that fully saturated fats are associated with problems of atherosclerosis and arterial fatty deposit, but there is evidence that stearates, which are saturates, are only poorly utilized in human digestion. Another body of work has estabUshed a connection between unsaturated fatty acids and a better state of arterial health and lowered fat body attachment to the arterial wall (23) contrary evidence exists that highly unsaturated fats polymerize more readily and thus contribute to arterial plaque formation. 

Synergists. The effect of antimony oxide on the flammabiUty of unsaturated polyesters that contain chlorine is shown in Table 11. A similar effect on the flammabiUty of unsaturated polyester containing 2inc stannates and bromine instead of chlorine is given in Table 12. 

Table 11. Effect of Chlorine and Antimony Oxide on the Oxygen Index of Unsaturated Polyesters...

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