2. Molecular Representations

How many hydrogens would you expect a 24-carbon compound from each of the following molecular classes to have?

(c) Alkyne

How many hydrogens would you expect a 24-carbon compound from each of the following molecular classes to have?

(b) Alkene

How many hydrogens would you expect a 24-carbon compound from each of the following molecular classes to have?

(a) Alkane

a. How many hydrogens does an alkane with 17 carbons have?

b. How many carbons does an alkane with 74 hydrogens have?

a. How many primary carbons does each of the following compounds have?

b. How many secondary carbons does each one have?

c. How many tertiary carbons does each one have?

2.

Macrolide antibiotics all have large rings (macrocycle) in which an ester makes the ring; a cyclic ester is termed a lactone. One example is erythromycin A, first isolated from soil bacteria in the 1950s. Over time, some pathogenic bacteria have developed resistance to erythromycin by evolving an enzymatic mechanism to cleave the macrocycle at the ketone. To counter this resistance, chemists modified the erythromycin structure to replace the ketone with an amine that the bacteria could not detoxify. This modified antibiotic, azithromycin, trade name Zithromax®, is one of the most prescribed drugs in the world for respiratory infections.

(c) Identify the ketone in erythromycin targeted by bacteria as the site for detoxification.

(d) Identify the amine in azithromycin. What type of amine is it?

Draw a Lewis structure, and classify each of the following compounds:

(g) (CH₃)₃CCH₂CH₂COOH

(h)

Many naturally occurring compounds contain more than one functional group. Identify the functional groups in the ­following compounds:

a. Penicillin G is a naturally occurring antibiotic.

b. Dopamine is the neurotransmitter that is deficient in Parkinson’s disease.

Many naturally occurring compounds contain more than one functional group. Identify the functional groups in the ­following compounds:

d. Thyroxine is the principal thyroid hormone.

There are eight different five-carbon alkyl groups.

c. In each case, label the degree of substitution (primary, secondary, or tertiary) of the head carbon atom bonded to the main chain.

When we begin studying functional groups, the designation of substitution will be especially important. Label the following bromoalkanes as 1° , 2°, 3°, or 4° based on the carbon to which the bromine is attached.

(b)