Alkanes, Alkynes, and Aromatic Compounds

Know how an alkene and alkyne differ from an alkane.

1) Alkenes are hydrocarbons that contain carbon-carbon double bonds. 2) Alkynes are hydrocarbons that contain carbon-carbon triple bonds.

Are the boiling points of alkanes lower or higher than those of almost any other type of compound of the same molecular weight? In general, do the boiling and melting points of alkanes increase or decrease with increasing molecular weight?

1) Boiling points of alkanes are lower than those of almost any other type of compound of the same molecular weight. 2) increase

Explain cis-trans stereoisomerism in alkenes. Be able to identify cis double bonds and trans double bonds.

1) In a cis isomer, the two groups are on the same side of the double bond. 2) In a trans isomer, they are on opposite sides of the double bond. 3) Cis-trans isomerism is possible whenever an alkene has two different substituent groups on each of its ends.

Lipids play three major roles in human biochemistry that allow us to classify them by function. List these categories.

1) Storage lipids 2) Membrane lipids 3) Specific biological activities (e.g. signals, cofactors, pigments, antioxidants)

Define aromatic compound. What is the structure of benzene?

1) The class of compounds containing benzene-like rings 2) a flat, symmetrical molecule with the molecular formula C6H6.

Define hydrocarbon and alkane.

1) hydrocarbon: organic compounds that contain only carbon and hydrogen. 2) have only single bonds and contain no functional groups

What are the physical properties of alkanes? (6)

1) nonpolar C-C and C-H bonds. 2) the melting and boiling points of straight-chain alkanes increase with molecular size. 3) Odorless or mild odor, colorless, tasteless, nontoxic 4) insoluble in water but soluble in nonpolar organic solvents, less dense than water 5) Flammable, otherwise not very reactive 6) saturated

What is the difference in structure between a saturated hydrocarbon and an unsaturated hydrocarbon?

1) saturated hydrocarbons in which all hydrogen atoms and carbon atoms are bonded together with single bonds, 2) unsaturated hydrocarbons have double or even triple bonds between the carbon atoms

What are the physical properties of alkenes and alkynes? (6)

1) unsaturated because they contain carbon-carbon multiple bonds. 2) Nonpolar; insoluble in water; soluble in nonpolar organic solvents 3) Less dense than water 4) Flammable; nontoxic 5) Alkenes display cis-trans isomerism when each double-bond carbon atom has different substituents. 6) Chemically reactive at the multiple bond

Unlike the case with protein, we define lipids in terms of a property and not in terms of their structure. What makes a molecule a lipid?

Lipids are defined by solubility in nonpolar solvents (a physical property) rather than by chemical structure.