shape and structure of organic compounds
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For this reason, ball-and-stick models or their equivalent are more generally useful than the space-filling models for visualizing structures and the positions of the atoms relative to one another. As we noted, there are several different kinds of hydrocarbons. For many purposes, ball-and-stick models of organic compounds give useful information about the spatial relationships of the atoms, and for $$CX_4$$ the angles between sticks are set at $$109.5^\text{o}$$ (Figure 2-1). Several bent bonds are required to construct models of compounds containing these units. An alkyl group is a group of atoms that results when one hydrogen atom is removed from an alkane. As we noted, there are several different kinds of hydrocarbons. For example, the molecular formula C4H10 tells us there are 4 carbon atoms and 10 hydrogen atoms in a molecule, but it doesn’t distinguish between butane and isobutane. We begin our study of organic chemistry with the hydrocarbons, the simplest organic compounds, which are composed of carbon and hydrogen atoms only. An ordinary solid line indicates a bond in the plane of the page. The name is 2,5-dimethylhexane. In our study of organic chemistry, it will become extremely important to be able to quickly recognize the most common functional groups, because they are the key structural elements that define how organic molecules react. The name indicates two methyl (CH3) groups, one on the second carbon atom and one on the third. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. If you are on a personal connection, like at home, you can run an anti-virus scan on your device to make sure it is not infected with malware. The size and shape of molecules are as much a part of molecular structure as is the order in which the component atoms are bonded. Thus Table 2-1 shows that single $$C-C$$ bonds become progressively shorter as the number of multiple bonds or electronegative atoms attached to the carbons increases. We first introduced the idea of the functional group, a specific structural arrangement of atoms or bonds that imparts a characteristic chemical reactivity to the molecule. The word saturated has the same meaning for hydrocarbons as it does for the dietary fats and oils: the molecule has no carbon-to-carbon double bonds (C=C). Different compounds having the same molecular formula are called isomers , and the prevalence of organic isomers reflects the extraordinary versatility of carbon in forming strong bonds to itself and to other elements. Alkanes have both common names and systematic names, specified by IUPAC. Adding the groups at their proper positions gives. Organic fertilizer, such as cow manure, is organic in the original sense; it is derived from living organisms. A particular functional group will almost always display its characteristic chemical behavior when it is present in a compound. It is not easy to visualize the possible arrangements of the bonds in space and it is very helpful to have some kind of mechanical model that reflects the molecular geometry, including at least an approximation to the relative lengths of the bonds. Organic compounds, like inorganic compounds, obey all the natural laws. Condensed chemical formulas show the hydrogen atoms (or other atoms or groups) right next to the carbon atoms to which they are attached. Now we examine some of the many organic compounds that contain functional groups. The vital force theory began to decline in 1828, when the German chemist Friedrich Wöhler synthesized urea from inorganic starting materials. • Recall that the VSEPR theory correctly predicts a tetrahedral shape for the methane molecule (Figure $$\PageIndex{2}$$). Any family of compounds in which adjacent members differ from each other by a definite factor (here a CH2 group) is called a homologous series. 26.1: Organic Compounds and Structures: An Overview, Organic Chemistry With a Biological Emphasis, low solubility in water; high solubility in nonpolar solvents, greater solubility in water; low solubility in nonpolar solvents, aqueous solutions do not conduct electricity. For now, we will consider only those substituents called alkyl groups. The word organic has different meanings. The sequence starts with C3H8, and a CH2 unit is added in each step moving up the series. Watch the recordings here on Youtube! Models of ethene and methanal can be built with ball-and-stick models by using flexible couplings or bent sticks to form the double bonds (Figure 2-2), but the $$H-C-H$$ angles are inaccurate because they are $$109.5^\text{o}$$ rather than the observed $$117^\text{o}$$ to $$118^\text{o}$$.