Molecular formulas defined

Molecular formulae define the atomic comptisition of compounds, but not the relative positions of the atoms. In addition, molecular formulae are not specific to a. single compound, but may be identical for many compounds with very different structures. 

What particularly seemed to excite Wohler and his mentor Berzelius about this experiment had very little to do with vitalism Berzelius was interested m cases m which two clearly different materials had the same elemental composition and he invented the term isomerism to define it The fact that an inorganic compound (ammonium cyanate) of molecular formula CH4N2O could be transformed into an organic compound (urea) of the same molecular formula had an important bearing on the concept of isomerism... 

Historically carbohydrates were once considered to be hydrates of carbon because their molecular formulas m many (but not all) cases correspond to C (H20) j It IS more realistic to define a carbohydrate as a polyhydroxy aldehyde or polyhydroxy ketone a point of view closer to structural reality and more suggestive of chemical reactivity... 

Answers from aH of these searches contain CAS Registry Numbers. Answer sets may be combined, using the Boolean operators AND, OR, or NOT, with other answer sets or with text terms, such as names or molecular formulas. Any answer set also may be used to define subsets of the file for subsequent stmcture searching. Answer sets of up to 10,000 Registry Numbers from any type of search in this file may also be used as search terms in other files, such as the CA or CAOLD files (53). 

Phosphoric acids and the phosphates maybe defined as derivatives of phosphoms oxides where the phosphoms atom is in the +5 oxidation state. These are compounds formed in the M2O—P20 system, where M represents one cation equivalent, eg, H", Na", 0.5 Ca ", etc. The molecular formula of the phosphoms(V) oxide [1314-56-3] is actually P O q, but this oxide is commonly referred to in terms of its empirical formula, P2O5. StmcturaHy, four phosphoms—oxygen (P—O) linkages are arranged in an approximate tetrahedral configuration about the phosphoms atom in the phosphate anion. Compounds containing discrete, monomeric PO ions are known as orthophosphates or simply as phosphates. 

Within each analogous series of hydrocarbons there exist isomers of the compounds within that series. An isomer is defined as a compound with the same molecular formula as another compound but with a different structural formula. In other words, if there is a different way in which the carbon atoms can align themselves in the molecule, a different compound with different properties will exist. 

Which one of the following could possibly be defined as the ratio of moles of each of the given elements to moles of each of the others (a) Empirical formula, (b) molecular formula, or (c) percent composition by mass. 

The index of hydrogen deficiency is defined as the number of pair of hydrogen atoms that must be subtracted from the molecular formula of the corresponding alkane to give the molecular formula of the compound under consideration. 

When a chemist writes down a molecular formula, it normally represents an ensemble of many molecules. The new challenge is to handle single molecules or defined aggregates of a few molecules. One would then want to visualize these nanoobjects, to move them around in real space, to record physical functions such as light emission and their response to a stimulus, and even to perform chemical reactions on them. 

Within the context of the Bom-Oppenheimer approximation, the potential energy surface may be regarded as a property of an empirical molecular formula. With a defined PES, it is possible to formulate and solve Schrodinger equations for nuclear motion (as opposed to electronic motion)... 

The phenomenon of isomerism, that is the existence of isomers, may be simply defined as the fact that molecules of identical elemental composition may exist in forms with different chemical or physical properties. Given that identity of chemical composition includes the specification of identical molecular formulae, the most obvious possible cause of differences in properties is a difference between isomers in the relative spatial distribution of their component atoms. Thus, the study of stereochemistry originated from attempts to understand isomerism.2... 

The map can be finite or infinite and some holes can be i-gons with i e R. If R = r, then the above definition corresponds to (r, q)gen-polycycles. If an (R, q)gen-polycycle is simply connected, then we call it an (R, )-polycycle those polycycles can be drawn on the plane with the holes being exterior faces. (R, )-polycycles with R = r are exactly the (r, interior faces is that polycyclic hydrocarbons in Chemistry have a molecular formula, which can modeled on such polycycles, see Figure 7.1. The definition of (R, < )-polycycles given here is combinatorial we no longer have the cell-homomorphism into r, q). We will define later on elliptic,... 

Diastereomers are defined as compounds which have the same molecular formula and sequence of bonded elements but which are nonsuperimposable, non-mirror... 

The appendix covers the period from mid-1984 to mid-1986, as defined by Chemical Abstracts coverage (Volumes 101-104). The structure designations and the reference numbering of the main body of the chapter are retained, and the presentation follows the same format but in less detail. No tabulation is given for new alkaloids in this section, but CA registry numbers (if assigned) and molecular formulas are included in the discussion. For our immediate purposes an alkaloid or botanical source is defined as new if it is not described in Chemical Abstracts prior to Volume 101. 

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