Using Protection

You can protect either a whole workbook or a worksheet within a workbook. Within a worksheet, you can lock cells so that they cannot be changed, and you can hide cells so that the user can t view the cell contents. 

The process for doing this is somewhat complicated. First you select cells to be locked and/or hidden, and set their status using the Protection tab of the Cells... command in the Format menu. Then you put the status into effect by choosing the Protection command in the Tools menu. 

Before you begin, it s important to know that when a new worksheet is opened, the status of all cells in the document is Locked. Thus if you select a range of cells to be locked, and set the status using Protect Sheet. you will find that all cells in the document are locked. 

To lock only a limited range of cells in a document (as you will most often want to do), you must first set the status of all the cells in the document to Unlocked and then select the range of cells that you want to be locked. 

Select all cells in the document by clicking on the row/column header button in the upper left comer of the worksheet. 

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The most commonly used protected derivatives of aldehydes and ketones are 1,3-dioxolanes and 1,3-oxathiolanes. They are obtained from the carbonyl compounds and 1,2-ethanediol or 2-mercaptoethanol, respectively, in aprotic solvents and in the presence of catalysts, e.g. BF, (L.F. Fieser, 1954 G.E. Wilson, Jr., 1968), and water scavengers, e.g. orthoesters (P. Doyle. 1965). Acid-catalyzed exchange dioxolanation with dioxolanes of low boiling ketones, e.g. acetone, which are distilled during the reaction, can also be applied (H. J. Dauben, Jr., 1954). Selective monoketalization of diketones is often used with good success (C. Mercier, 1973). Even from diketones with two keto groups of very similar reactivity monoketals may be obtained by repeated acid-catalyzed equilibration (W.S. Johnson, 1962 A.G. Hortmann, 1969). Most aldehydes are easily converted into acetals. The ketalization of ketones is more difficult for sterical reasons and often requires long reaction times at elevated temperatures. a, -Unsaturated ketones react more slowly than saturated ketones. 2-Mercaptoethanol is more reactive than 1,2-ethanediol (J. Romo, 1951 C. Djerassi, 1952 G.E. Wilson, Jr., 1968). 

A widely used protecting agent is 2-cyanoethanol (- 3-hydroxypropanonitrile, hy-dracrylonitrile), which is condensed with phosphates with the aid of DCC. The 2-cyanoethyl (Ce) group is quantitatively removed as acrylonitrile by treatment with weak bases (H.G. Kho-rana, 1965). 

It is widely recognized that an allyl group is a useful protecting group for acids, amines, and alcohols. Facile formation of a Tr-allylpalladium complex from... 

Oriented polypropylene film (OPP) may be classified as heat-set and non-heat-set, blown and tentered, coextmded and coated. Orientation improves the cold-temperature resistance and other physical properties. Heat-set biaxially oriented polypropylene film (BOPP) is the most widely used protective packagiag film ia the United States. It is used to wrap bakery products, as lamination pHes for potato and com chips, and for pastas and numerous other flexible pouch and wrapping appHcations. Nonheat-set OPP is used as a sparkling, transparent shrink-film overwrap for cartons of candy. 

Poly(vinyl acetate) emulsions can be made with a surfactant alone or with a protective coUoid alone, but the usual practice is to use a combination of the two. Normally, up to 3 wt % stabilizers may be included in the recipe, but when water sensitivity or tack of the wet film is desired, as in some adhesives, more may be included. The most commonly used surfactants are the anionic sulfates and sulfonates, but cationic emulsifiers and nonionics are also suitable. Indeed, some emulsion compounding formulas require the use of cationic or nonionic surfactants for stable formulations. The most commonly used protective coUoids are poly(vinyl alcohol) and hydroxyethyl cellulose, but there are many others, natural and synthetic, which are usable if not preferable for a given appHcation. 

Ethers are among the most used protective groups in organic synthesis. They vary from the simplest, most robust, methyl ether to the more elaborate, substituted, trityl ethers developed for use in nucleotide synthesis. They are formed and removed under a wide variety of conditions. Some of the ethers that have been used to protect alcohols are included in Reactivity Chart 1. ... 

The introduction of a THP ether onto a chiral molecule results in the formation of diastereomers because of the additional stereogenic center present in the tetrahy-dropyran ring (which can make the interpretation of NMR spectra somewhat troublesome at times). Even so, this is one of the most widely used protective groups employed in chemical synthesis because of its low cost, the ease of its installation, its general stability to most nonacidic reagents, and the ease with which it can be removed. 

Acetonide formation is the most commonly used protection for 1,2- and 1,3-diols. The acetonide has been used extensively in carbohydrate chemistiy to mask selectively the hydroxyls of the many different sugars. In preparing acetonides of triols, the 1,2-derivative is generally favored over the 1,3-derivative, but the extent to which the 1,2-acetonide is favored is dependent on stmcture. Note that the 1,2-selectivity for the ketal from 3-pentanone is better than that from acetone. ... 

A benzylidene acetal is a commonly used protective group for 1,2- and 1,3-diols. In the case of a 1,2,3-triol the 1,3-acetal is the preferred product. It has the advantage that it can be removed under neutral conditions by hydrogenolysis or by acid hydrolysis. Benzyl groups and isolated olefins have been hydrogenated in the presence of 1,3-benzylidene acetals. Benzylidene acetals of 1,2-diols are more susceptible to hydrogenolysis than are those of 1,3-diols. In fact, the former can be removed in the presence of the latter. A polymer-bound benzylidene acetal has also been prepared." ... 

In this chapter detailed information is pn vided for the more useful protective groups (some of which are included in Reactivity Charts 8-10) structures and references are given for protective groups that seem to have more limited use. ... 

Use protective/barrier creams and skin reconditioning creams Maintain high standard of personal hygiene... 

Cutaneous Cutaneous relates to or affects the skin. The term subcutaneous refers to being below the skin (as in a penetrating injury or injection). Use your MSDS to determine the required personal protective equipment (PPE) that you must use. Protecting the skin (with gloves, aprons, coveralls, face masks, etc.) is important. After all, the skin is the largest organ in the human body. 

Alkyds are the most widely used protective-coatings at 1-million pounds annual world consumption. Brittle and insoluble in common solvents, they are manufactured with a plasiici/m. -Manipulating the molecular structure produces alkyds with the desirable properties. 

Filters should be replaced carefully, using protective equipment so that the impurities trapped do not escape. 

To avoid injuries of this sort, we should use protective hoods or helmets when breaking joints on lines likely to contain corrosive liquids trapped under pressure, either because the pressure cannot be blown off through a valve or because lines may contain solid deposits. 

Silyl ethers are among the most frequently used protective groups for the alcohol function. This stems largely from the fact that their reactivity (both formation and cleavage) can be modulated by a suitable choice of substituents on the silicon atom. Both steric and electronic effects are the basic controlling elements that regulate the ease of cleavage in multiply functionalized substrates. In plan-... 

All the approaches for deblocking protective groups described earlier in this book have found application in the removal of protective groups from phosphorus derivatives. Because phosphate protection and deprotection are commonly associated with compounds that contain acid-sensitive sites (e.g., glycosidic linkages and DMTr-O- groups of nucleotides), the most widely used protective groups on phosphorus are those that are deblocked by base. 

Normally a specialist works application these materials are useful protective coatings for such items as cable trays and switch boxes. They are also used for the externals of pipelines. 

The modern procedure to minimise corrosion losses on underground structures is to use protective coatings between the metal and soil and to apply cathodic protection to the metal structure (see Chapter 11). In this situation, soils influence the operation in a somewhat different manner than is the case with unprotected bare metal. A soil with moderately high salts content (low resistivity) is desirable for the location of the anodes. If the impressed potential is from a sacrificial metal, the effective potential and current available will depend upon soil properties such as pH, soluble salts and moisture present. When rectifiers are used as the source of the cathodic potential, soils of low electrical resistance are desirable for the location of the anode beds. A protective coating free from holidays and of uniformly high insulation value causes the electrical conducting properties of the soil to become of less significance in relation to corrosion rates (Section 15.8). 

Paint is the most widely used protective coating for steelwork and normally acts as a barrier between the metal and environment. The choice of type of paint and the final thickness required depends on the conditions of service, and the more severe the conditions the thicker and more resistant the paint film needs to be. Also the more sophisticated the paint system the more demanding is the surface preparation required. 

Two recent reports described addition of nitrogen-centered nucleophiles in usefully protected fonn. Jacobsen reported that N-Boc-protected sulfonamides undergo poorly selective (salen) Co-catalyzed addition to racemic epoxides. However, by performing a one-pot, indirect kinetic resolution with water first (HKR, vide infra, Table 7.1) and then sulfonamide, it was possible to obtain highly enantiomer-ically enriched addition products (Scheme 7.39) [71]. These products were transformed into enantioenriched terminal aziridines in straightforward manner. 

The superiority of LiAsF6 in ether based solvents (2-Me-THF, THF, MeF) at lithium electrodes is an example of the formation of useful protecting films (As, Li2 As, Li (AsFv) allowing uniform lithium deposition [195], According to Aur-bach and co-workers, LiAsF6/2 - Me -THF is a highly suitable electrolyte for rechargeable lithium batteries. However, as 2-Me-THF is one of the least reactive sol-... 

Thus, heterobifunctional cyclohexadienes are accessible from benzene by temporary complexation to Fe2+ which reverses the reactivity of the aromatic. Double nucleophilic attack is possible but only using protection-deprotection by hydride. 

Endosulfan and metabolites were observed in the urine of workers who had prepared and applied endosulfan for 2-5 hours either 1 day or 1 week prior to sampling, without using protective clothing or face mask (thus, exposure was probably both dermal and inhalation) (Vidal et al. 1998). Unchanged a-and P-endosulfan and endosulfan ether were the predominant chemicals excreted 1 day following exposure. One week after exposure, a-endosulfan was detected in urine of four of five workers, but P-endosulfan was detected in only one of five samples and endosulfan ether was not detected at all. Endosulfan sulfate was detected in only one of five samples at 1 week after exposure and in none of the four samples at 1 day postexposure. Endosulfan lactone was detected in one of four and one of five samples at 1 day and 1 week after exposure, respectively. 

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