Olestra is a fat substitute that has the properties of a fat in flavor and texture, but is indigestible - hence a fake fat. In 1996, the FDA approved the use of olestra in potato chips, tortilla chips, crackers and fried snacks, as it is the only heat stable fat substitute for fried foods. Since olestra is such a large nonpolar molecule, it may dissolve or combine with some of the fat soluble vitamins such as A, D, E, and K, and carotenoids.
The reduction half cell is Eqn 2, and shows 6 e-. The form of the oxidation half cell that is convenient here is Eqn 12; it shows 4 e-. To get the electrons to balance out when the two are combined, we take 2 times Eqn 2, and add 3 times Eqn 12. For CH 3 CH 2 OH , there are 6 H = 6+ and 1 O = 2-. Total of H and O is 4+, therefore the total ON for the two C atoms is 4-. Similarly, for CH 3 COOH, the total ON for the two C atoms is 0.
If E is a strong electrophile, as in the first equation, it will attack the nucleophilic oxygen of the carboxylic acid directly, giving a positively charged intermediate which then loses a proton. If E is a weak electrophile, such as an alkyl halide, it is necessary to convert the carboxylic acid to the more nucleophilic carboxylate anion to facilitate the substitution. The reaction is easily followed by the evolution of nitrogen gas and the disappearance of the reagent's color.
Although nitriles do not have a carbonyl group, they are included here because the functional carbon atoms all have the same oxidation state. The top row (yellow shaded) shows the general formula for each class, and the bottom row (light blue) gives a specific example of each. As in the case of amines, amides are classified as 1º, 2º or 3º, depending on the number of alkyl groups bonded to the nitrogen. The Greek letter locates the nitrogen relative to the carbonyl group of the amide.
Recall that the molecular formula of a hydrocarbon (C n H m ) provides information about the number of rings and/or double bonds that must be present in its structural formula. These are illustrated by the examples in the table above, taken from the previous list of naturally occurring amines. • The presence of oxygen does not alter the relationship. • All halogens present in the molecular formula must be replaced by hydrogen. • Each nitrogen in the formula must be replaced by a CH moiety.
The stereoselectivity of Brønsted acid addition is sensitive to experimental conditions such as temperature and reagent concentration. The selectivity is often anti, but reports of syn selectivity and non-selectivity are not uncommon. Of all the reagents discussed here, these strong acid additions (E = H in the following equation) come closest to proceeding by the proposed two-step mechanism in which a discrete carbocation intermediate is generated in the first step.
We can account both for the high stereoselectivity and the lack of rearrangement in these reactions by proposing a stabilizing interaction between the developing carbocation center and the electron rich halogen atom on the adjacent carbon. The positive charge is delocalized over all the atoms of the ring, but should be concentrated at the more substituted carbon (carbocation stability), and this is the site to which the nucleophile will bond.
Since boron is electron deficient (it does not have a valence shell electron octet) the reagent itself is a Lewis acid and can bond to the pi-electrons of a double bond by displacement of the ether moiety from the solvated monomer. Indeed, this hydride shift is believed to occur concurrently with the initial bonding to boron, as shown by the transition state drawn below the equation, so the discrete intermediate shown in the equation is not actually formed.
The line extending off without anything connected is the line that shows this is a group, which should be attached to something. For example, one might have phenyl chloride (C 6 H 5 Cl, also called chlorobenzene) or one might have benzyl chloride (C 6 H 5 CH 2 Cl). (The structures of these two compounds are shown below in Figure 2.) The phenyl group is based simply on benzene, with one H removed. The benzyl group is based on methylbenzene (toluene), with one H removed from the methyl group.