Cycloalkanes Cyclic saturated hydrocarbons

Cycloalkanes are cyclic saturated hydrocarbons with the general formula C H2 . Therefore, a substance with the formula C3H8 could not be a cycloalkane, since C3H8 conforms to the general formula, C H2 +2, the molecular formula for an alkane. It is, however, too small to be a branched alkane with a methyl group attached to the longest chain. In fact, C3H8 is propane. 

Cycloalkanes arc a got up of cyclic saturated hydrocarbons with a general formula of Which of the... 

The cyclic saturated hydrocarbons, or cychalkanes, have the general formula C 2n-cycloalkanes (and other ring compounds that we will encounter later) are often shown in simplified skeletal form in which each intersection of two lines represents a C atom we mentally add enough H atoms to give each carbon atom four bonds. The first four unsubstituted cycloalkanes and their simplified representations are... 

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... 

The alkanes are acyclic, saturated hydrocarbons that form a homologous series of compounds, with the general formula C H2 +2, The cycloalkanes are cyclic, saturated hydrocarbons that form another homologous series with the general formula C H2 in which the carbon atoms are joined in a ring. The... 

Cycloalkane a cyclic saturated hydrocarbon that is, a saturated hydrocarbon in which the carbon atoms form a ring the general formula is C H2 . (24.2)... 

P450 are found in complex molecules as well as in saturated hydrocarbons (alkanes and cycloalkanes). For example, the steroid progesterone is hydroxylated in positions 11(3, 17a and 21 to yield hydrocortisone. In practice, a nonactivated aUcyl group undergoes mainly to- and co - 1 oxidation. On the other hand, n-hexadecane is co-hydroxylated in the liver to yield hexadecanol which is further oxidized to hexadecanoic acid. For shorter chains, both terminal and (0 — 1 oxidations are observed (Fig. 31.5). Cyclic aliphatic systems are usually hydroxylated on the least hindered or most activated carbon atoms. 

The idea that carbon atoms can be bound in cyclic structures (besides forming chains and branched chains) appeared during the second half of nineteenth century. When these cyclic structures are saturated hydrocarbons we talk about cycloalkanes. In the nomenclature of this class of compounds the name is formed by adding the prefix cyclo-. 

Saturated hydrocarbons are known as alkanes if they are acyclic, or as cycloalkanes if they are cyclic. Let us look at their structures and properties. 

We JI look in the next chapter at cycloalkanes—saturated cyclic hydrocarbons— and we ll see that the molecules generally adopt puckered, nonplanar conformations. Cyclohexane, for instance, has a puckered shape like a lounge chair rather than a flat shape. Why ... 

Saturated cyclic hydrocarbons are called cycloalkanes, or alicyclic compounds (aliphatic cyclic). Because cycloalkanes consist of rings of -CH2- units, they have the general formula (CH2) , or and can be represented by polygons... 

A cycloalkane is a saturated cyclic hydrocarbon with the general formula C H2 . In contrast to open-chain alkanes, where nearly free rotation occurs around C, -C bonds, rotation is greatly reduced in cycloalkanes. Disubstituted cycloalkanes can therefore exist as cis-trans isomers. The cis isomer has both substituents on the same face of the ring the trans isomer has substituents on opposite faces. Cis-trans isomers are just one kind of stereoisomers—isomers... 

The simplest of the saturated cyclic hydrocarbons, or cycloalkanes, is cyclopropane, C3Hg, the molecules of which are made up of three carbon atoms to each of which two hydrogen atoms are attached. Cyclopropane is somewhat more reactive than the corresponding open-chain alkane, propane, C3Hg. Other cycloalkanes make up a part of ordinary gasoline. 

The product consists uf various amounts of high polymer (.r is very large) and discrete cyclosilanes with n = 5-35. This is the largest homologous series of cyclic compounds now known except for the cycloalkanes. Although these compounds are formally saturated, they behave in some ways as aromatic hydrocarbons. They can be reduced to amon ladicals. and EPR spectra indicate that the unpaired electron is delocalized over the entire ring. 06... 

Additionally, classes (or types) of hydrocarbons were, and still are, determined based on the capability to isolate them by separation techniques. The four fractional types into which petroleum is subdivided are paraffins, olefins, naphthenes, and aromatics (PONA). Paraffinic hydrocarbons include both normal and branched alkanes, whereas olefins refer to normal and branched alkenes that contain one or more double or triple carbon-carbon bonds. Naphthene (not to be confused with naphthalene) is a term specific to the petroleum industry that refers to the saturated cyclic hydrocarbons (cycloalkanes). Finally, the term aromatics includes all hydrocarbons containing one or more rings of the benzenoid structure. 

A hydrocarbon that contains carbon atoms joined to form a ring is called a cyclic hydrocarbon. When all carbons of the ring are saturated, we call the hydrocarbon a cycloalkane. Cycloalkanes of ring sizes ranging from 3 to over 30 abound in nature, and, in principle, there is no limit to ring size. Five-membered (cyclopentane) and six-membered (cyclohexane) rings are especially abundant in nature and have received special attention. 

---