Chapter 11-Intro to Organic Molecules and Functional Groups

Skeletal structures are used for organic compounds containing both rings and chains of atoms.

Assume there is a carbon atom at the junction of any two lines or at the end of any line. Assume there are enough hydrogens around each carbon to give it four bonds. Draw in all heteroatoms and the hydrogens directly bonded to them.

Organic compounds exist as discrete molecules with much weaker intermolecular forces—the forces that exist between molecules—than those seen in ionic compounds, which are held together by very strong interactions of oppositely charged ions.

As a result, organic compounds resemble other covalent compounds in that they have much lower melting points and boiling points than ionic compounds.

Moreover, because organic molecules often contain many atoms, we use shorthand methods to simplify them.

As a result, pentane can also be represented by the condensed structure C and the skeletal structure D.

An atom surrounded by three groups is trigonal planar and has a bond

angle of 120°.

An atom surrounded by two groups is linear and has a bond

angle of 180°.

An atom surrounded by four groups places these four groups at the corners of a tetrahedron, giving bond

angles of approximately 109.5°

vitamins

are organic compounds needed in small amounts for normal cell function

shows examples of converting cyclic skeletal structures into

complete structures.

Carbon forms

single, double, and triple bonds to other carbon atoms.

One rule governs solubility: "Like dissolves like." Three facts can then be used to explain the solubility of organic compounds.

-Most organic compounds are soluble in organic solvents. -Hydrocarbons and other nonpolar organic compounds are not soluble in water. -Polar organic compounds are water soluble only if they are small (less than six carbons) and contain a nitrogen or oxygen atom that can hydrogen bond with water.

Hydrocarbons

11.5) A compound that contains only the elements of carbon and hydrogen. are compounds that contain only the elements of carbon and hydrogen, as shown in Table 11.2.

A C atom surrounded by four atoms forms four single bonds. In ethane (C2H6), each carbon atom is bonded to three hydrogen atoms and one carbon atom. All bonds are single bonds. A C atom surrounded by three atoms forms one double bond. In ethylene (C2H4), each carbon atom is surrounded by three atoms (two hydrogens and one carbon); thus, each C forms a single bond to each hydrogen atom and a double bond to carbon.

A C atom surrounded by two atoms generally forms one triple bond. In acetylene (C2H2), each carbon atom is surrounded by two atoms (one hydrogen and one carbon); thus, each C forms a single bond to hydrogen and a triple bond to carbon. [3] Some compounds have chains of atoms and some compounds have rings.

If the individual bond dipoles cancel in a molecule, the molecule is nonpolar. If the individual bond dipoles do not cancel, the molecule is polar.

A bond dipole can be indicated by an arrow with the head of the arrow pointing toward the more electronegative element, and a perpendicular line drawn through the tail of the arrowPage 412 (). Thus, dichloroacetylene (ClC≡CCl) is a linear molecule with two polar C—Cl bonds, but the individual bond dipoles are equal in magnitude and opposite in direction. As a result, dichloroacetylene is a nonpolar molecule. In contrast, methanol, CH3OH, has two polar bonds (C—O and O—H), and a bent shape around oxygen (Section 11.3). The individual bond dipoles do not cancel, so CH3OH is a polar molecule.

A solid line is used for bonds in the plane. A wedge is used for a bond in front of the plane.

A dashed wedge is used for a bond behind the plane.

Alkanes have only C─C single bonds and no functional group. Ethane, CH3CH3, is a simple alkane. Alkenes have a C─C double bond as their functional group. Ethylene, CH2═CH2, is a simple alkene.

Alkynes have a C─C triple bond as their functional group. Acetylene, HC≡CH, is a simple alkyne. Aromatic compounds contain a benzene ring, a six-membered ring with three double bonds.

Rings are drawn as polygons with a carbon atom "understood" at each vertex, as shown for cyclohexane and cyclopentanol.

All carbons and hydrogens in these molecules are understood, except for H's bonded to heteroatoms.

Organic compounds may also contain elements other than carbon and hydrogen.

Any atom that is not carbon or hydrogen is called a heteroatom.

All organic compounds contain carbon atoms and most contain hydrogen atoms.

Carbon always forms four covalent bonds, and hydrogen forms one covalent bond.

Like other covalent compounds, the polarity of an organic compound is determined by two factors: the polarity of the individual

Page 411 bonds and the overall shape of the molecule.

Each heteroatom forms a characteristic number of bonds, determined by its location in the periodic table.

The common heteroatoms also have nonbonding, lone pairs of electrons, so that each atom is surrounded by eight electrons.

The symbol δ+ is given to the less electronegative atom (usually C or H).

The symbol δ− is given to the more electronegative atom (usually N, O, or a halogen).

Many different kinds of compounds contain a carbon-oxygen double bond (C═O, carbonyl group), as shown in Table 11.4. Carbonyl compounds include aldehydes, ketones, carboxylic acids, esters, and amides.

The type of atom bonded to the carbonyl carbon—hydrogen, carbon, or a heteroatom—determines the specific class of carbonyl compound.

Condensed structures are most often used for a compound having

a chain of atoms bonded together, rather than a ring.

organic chemistry

is the study of compounds that contain the element carbon.

To interpret a condensed formula, it is usually best to start at the

left side of the molecule and remember that the carbon atoms must have four bonds.