Alkanes molecular formula

Examples of the general alkane molecular formula, CnH2n+2-... 

Identify the Alkane molecular formula for six carbons. For n = 6 we would have CnH2n+2 That would be CeHu. 

Alkanes have the general molecular formula C H2 +2 The srmplest one methane (CH4) rs also the most abundant Large amounts are present rn our atmosphere rn the ground and rn the oceans Methane has been found on Juprter Saturn Uranus Neptune and Pluto and even on Halley s Comet... 

Methane is the only alkane of molecular formula CH4 ethane the only one that is C2H6 and propane the only one that is C3Hj Beginning with C4H10 however constitutional isomers (Section 1 8) are possible two alkanes have this particular molecular formula In one called n butane, four carbons are joined m a continuous chain The nmn butane stands for normal and means that the carbon chain is unbranched The second isomer has a branched carbon chain and is called isobutane... 

An n alkane of molecular formula C28H58 has been isolated from a certain fossil plant Write a condensed structural formula for this alkane J... 

Much of the communication between insects involves chemical messengers called pheromones A species of cockroach secretes a substance from its mandibular glands that alerts other cockroaches to its presence and causes them to congregate One of the principal components of this aggregation pheromone is the alkane shown in the bond line formula that follows Give the molecular formula of this substance and represent it by a condensed formula... 

Three isomeric alkanes have the molecular formula C5H12 The unbranched isomer is as we have seen n pentane The isomer with a single methyl branch is called isopen tane The third isomer has a three carbon chain with two methyl branches It is called neopentane... 

The Number of Constitutionally Isomeric Alkanes of Particular Molecular Formulas... 

In Problem 2 5 you were asked to write structural formulas for the five isomeric alkanes of molecular formula C6H14 In the next section you will see how the lUPAC rules generate a unique name for each isomer... 

Cycloalkanes are alkanes that contain a ring of three or more carbons They are fre quently encountered m organic chemistry and are characterized by the molecular formula C H2 Some examples include... 

The classes of hydrocarbons are alkanes, alkenes, alkynes, and arenes Alkanes are hydrocarbons in which all of the bonds are single bonds and are characterized by the molecular formula C H2 +2... 

Two constitutionally isomeric alkanes have the molecular formula C4H10 One has an unbranched chain (CH3CH2CH2CH3) and is called n butane, the other has a branched chain [(CH3)3CH] and is called isobutane Both n butane and isobutane are common names... 

The general molecular formula for alkanes is C H2 +2 What is the general molecular for mula for... 

Wnte structural formulas and give the lUPAC names for the nine alkanes that have the molecular formula CyHig... 

Among the isomenc alkanes of molecular formula C5H12 identify the one that on photo chemical chlorination yields... 

Earlier (Sections 218 3 11) we saw how to use heats of combustion to compare the sta bilities of isomeric alkanes We can do the same thing with isomeric alkenes Consider the heats of combustion of the four isomenc alkenes of molecular formula C4Hj All undergo combustion according to the equation... 

The sex attractant by which the female housefly attracts the male has the molecular formula C23H46 Catalytic hydrogenation yields an alkane of molecular formula C23H4g Ozonolysis yields... 

What about a substance wrth the molecular formula 71414 Thrs compound can not be an alkane but may be erther a cycloalkane or an alkene because both these classes of hydrocarbons correspond to the general molecular formula C H2 Any time a ring or a double bond is present in an organic molecule its molecular formula has two fewer hydrogen atoms than that of an alkane with the same number of carbons... 

A molecule of molecular formula C7H12 has four fewer hydrogens than the corre spondrng alkane It has an rndex of hydrogen defrcrency of 2 and can have two rrngs two double bonds one rrng and one double bond or one trrple bond... 

Index of hydrogen deficiency (Section 13 23) A measure of the total double bonds and nngs a molecule contains It is determined by comparing the molecular formula C Hj. of the compound to that of an alkane that has the same number of carbons according to the equation... 

An analogous series of hydrocarbons, and one of the simplest, are the compounds known as the alkanes. In this series, the names of all the compounds end in -ane. The first compound in this series is methane. Methane s molecular formula is CH. Methane is a gas and is the principal ingredient in the mixture of gases known as natural gas. The next compound is this series is ethane, whose molecular formula is CjHj. It is also a gas present in natural gas, although in a much lower percentage than methane. The difference in the molecular formulas of methane and ethane is one carbon and two hydrogen atoms. 

The next six alkanes are named pentane, hexane, heptane, octane, nonane, and decane. Their molecular formulas are CjHij, C5H14, CjHjg, C Hjg and... 

There are two fewer hydrogen atoms in each of the alkenes than in the alkane with the same number of carbon atoms. This is also shown by the general molecular formula of the alkenes, C H2 , as opposed to the general molecular formula of the alkanes, which is C H2n+2-... 

The next simplest ether is the ether with the simplest alkane as one of the hydrocarbon backbones and the next alkane, which is methyl ethyl ether. Its molecular formula is CH3OC2H5. It is a colorless gas with the characteristic ether odor. It has a flash point of 31 °F, and an ignition temperature of only 374°F. This property, of course, makes it an extreme fire and explosion hazard. 

Isomers are substances having the same molecular formula and molecular weight, but differing in physical and chemical properties. Since branched and straight-chain alkanes with the same molecular formula can exist as distinct structures having different geometrical arrangement of the atoms, they are termed structural isomers. One example is C H,j (butane) which has two isomers ... 

In general, each ting or double bond in a molecule corresponds to a loss of two hydrogens from the alkane formula ChH2/1+2- Knowing this relationship, it s possible to work backward from a molecular formula to calculate a molecule s degree of unsaturation—the number of rings and/or multiple bonds present in the molecule. 

Let s assume that we want to find the structure of an unknown hydrocarbon. A molecular weight determination on the unknown yields a value of 82, which corresponds to a molecular formula of CfcHjo Since the saturated Q alkane (hexane) has the formula C61-114, the unknown compound has two fewer pairs of hydrogens (H]4 - H l() = H4 = 2 H2), and its degree of unsaturation is two. The unknown therefore contains two double bonds, one ring and one double bond, two rings, or one triple bond. There s still a long way to go to establish structure, but the simple calculation has told us a lot about the molecule. 

Two different alkanes are known with the molecular formula C Hm- In one of these, called butane, the four carbon atoms are linked in a straight (unbranched) chain. In the other, called 2-methylpropane, there is a branched chain. The longest chain in the molecule contains three carbon atoms there is a CH3 branch from the central carbon atom. The geometries of these molecules are shown in Figure 22.2 (p. 581). The structures are... 

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