Acyclic alkanes molecular formula

As with alkanes, the boiling points and melting points of alkenes decrease with increasing molecular weight, but show some variations that depend on the shape of the molecule. Alkenes with the same molecular formula are isomers of one another if the position and the stereochemistry of the double bond differ. For example, there are four different acyclic structures that can be drawn for butene (C4H8). They have different b.p. and m.p. as follows. 

Acyclic alkanes have the molecular formula C H2 +2 (where = an integer) and contain only linear and branched chains of carbon atoms. They are also called saturated hydrocarbons because they have the maximum number of hydrogen atoms per carbon. 

Problem 4.1 which molecular formulas correspond to an acyclic alkane a. C12H26 b. CbH-16 c. C3oHb4... 

There are two types of alkanes acyclic aikanes having molecular formula + 2, and cycloalkanes having molecular formula... 

An acyclic alkene has the general molecular formula C H2m giving it two fewer hydrogens than an acyclic alkane with the same number of carbons. 

In Chapter 2, you learned that the general molecular formula for a noncyclic alkane is C H2n+2- You also learned that the general molecular formula for a cyclic alkane is C H2 because the cyclic stmcture reduces the number of hydrogens by two. Noncyclic compounds are also called acyclic compounds ( a is Greek for non or not ). 

The general molecular formula for an acyclic alkene is also C H2 because, as a result of the carbon-carbon double bond, an alkene has two fewer hydrogens than an alkane with the same number of carbon atoms. Thus, the general molecular formula for a cyclic alkene must be C H2 -2- We can, therefore, make the following statement The general molecular formula for a hydrocarbon is C H2 +2, minus two hydrogens for every tt bond and/or ring in the molecule. 

Alkynes are hydrocarbons that contain a carbon-carbon triple bond. Because of its triple bond, an alkyne has four fewer hydrogens than the corresponding alkane. Therefore, the general molecular formula for an acyclic (noncyclic) alkyne is C H2 -2, and that for a cyclic alkyne is C H2 -4. 

What kind of structure might we predict for benzene if we knew only what the early chemists knew The molecular formula (CgHg) tells us that benzene has eight fewer hydrogens than an acyclic (noncyclic) alkane with six carbons (C H2 +2 = C6H14). Benzene, therefore, has a degree of unsaturation of four (Section 3.1). This means that benzene is either an acyclic compound with four tt bonds, a cyclic compound with three tt bonds, a bicyclic compound with two tt bonds, a tricyclic compound with one TT bond, or a tetracyclic compound. 

The molecular formula of a reference acyclic alkane is C 2n+i (Section 2.1). 

The molecular formula of the reference acyclic alkane of sbc carbon atoms is CgHj. The index of hydrogen deficiency of 1-hexene (14 - 12)/2 = 1 and is accounted for by the one tt bond in 1-hexene. 

All the hydrocarbons we have met so far have the molecular formula C H.2 + 2-Because these molecules are linear or branched chains, we refer to them as either noncyclic or acyclic alkanes. Molecules of this formula are also called saturated hydrocarbons, which means that the carbon-carbon bonds in the molecule are all single bonds. There is a class of closely related molecules that shares most chemical properties with the noncyclic alkanes but not the general formula. These molecules have the composition C H2 and are the cycloalkane ring compounds mentioned briefly in Section 2.1. Cycloalkanes with this formula are also saturated. Molecules that have the formula C H2 but have no rings are called unsaturated hydrocarbons. Unsaturated compounds have carbon-carbon double (or triple) bonds and will be discussed in Chapter 3. 

The alkanes are acyclic saturated hydrocarbons, and the cycloalkanes are cyclic saturated hydrocarbons. The simplest hydrocarbon, an alkane called methane, consists of one carbon atom to which four hydrogen atoms are bonded in a tetrahedral arrangement. You can represent methane by its molecular formula, CH4, which gives the number and kind of atoms in the molecule, or by its structural formula, which shows how the atoms are bonded to one another... 

How is this concept useful Let us say that we have isolated a hydrocarbon of molecular formula QHg. If this had been an acyclic alkane, we would have expected 2 + 2 hydrogens, in this case 14. So we are six hydrogens short. So we must have three rings or double bonds, for example, 3.3, 3.4, or 3.5. We can generalize this to say that if we have carbon atoms and m hydrogen atoms, then (DBE) = 2n + 2) - m /2. Halogens count as if they were hydrogens. 

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