chapter 4

Functional Groups

-A is an amino group, NH2. -B is a phosphate group. the only one that contains phosphorus. -D is a hydroxyl group -F a carboxyl group -D is characteristic of alcohol (Hydroxyl groups are characteristic of alcohol.) -A groups behaves as a base (The electronegativity of nitrogen means that amino groups tend to pick up hydrogen ions.) -E groups is characteristic of thiols. (Thiols are characterized by the presence of a sulfhydryl group.) -B groups plays a major role in energy transfer.(Phosphate groups are a component of ATP.) -C is a carbonyl group, and is characteristic of a ketone (A carbonyl group in the middle of a carbon skeleton characterizes ketones.) -F behaves as an acid (By donating hydrogen ions, carboxyl groups act as an acid.)

How many hydrogen atoms can be attached to carbon B?

1 A carbon atom can form up to four covalent bonds.

How many structural isomers are possible for a substance having the molecular formula C4H10?

2

How many hydrogen atoms can be attached to carbon A?

3 A carbon atom can form up to four covalent bonds.

How many electron pairs does carbon share in order to complete its valence shell?

4

Identifying functional groups in a molecule

A functional group is a group of atoms bonded together in a specific way that can replace a hydrogen atom in a hydrocarbon. The molecule shown here contains four functional groups (−OH, −SH, −NH2, and −OPO2−3) attached to a carbon chain that is six carbon atoms long.

Which statement about a methyl functional group is correct?

A methyl group consists of a carbon bonded to three hydrogen atoms. A methyl group consists of a carbon covalently bonded to three hydrogen atoms.

Identify the functional groups.

Amino and carboxyl are functional groups. Read about the variety of biologically important functional groups and note the structure and functional properties of amino and carboxyl groups.

Which of the following hydrocarbons has a double bond in its carbon skeleton?

C2H4

Which of the following is a hydrocarbon?

C3H8 This is a typical hydrocarbon with single covalent bonds; the number of hydrogen atoms is equal to two times the number of carbon atoms plus 2.

Which statement about isomers is correct?

Enantiomers differ in biological activity. Because enantiomers are mirror images of each other, working molecules distinguish the two versions by shape. Usually, one isomer is biologically active and the other is inactive.

Which of the following people was the first to synthesize an organic compound, urea, from inorganic starting materials?

Friedrich Wohler

How do isomers differ from one another?

Isomers differ in the arrangement or bonding of atoms. Isomers may differ in the covalent arrangements of their atoms or the position of double bonds within the molecule and thus have different chemical properties.

Hermann Kolbe's synthesis of an organic compound, acetic acid, from inorganic substances that had been prepared directly from pure elements was a significant milestone for what reason?

It proved that organic compounds could be synthesized from inorganic compounds and disproved the concept of vitalism.

A compound contains hydroxyl groups as its predominant functional group. Which of the following statements is true concerning this compound?

It should dissolve in water.

What kind of effect does R-dopa have on Parkinson's disease?

None. R-dopa has no effect on Parkinson's disease.

How do these hydrocarbons differ?

One of these hydrocarbons has a double bond. The hydrocarbon on the right has a double bond.

How do these hydrocarbons differ?

One of these hydrocarbons has a ring structure. The hydrocarbon on the right has a ring structure.

How do these hydrocarbons differ?

One of these hydrocarbons is branched. The hydrocarbon on the right is branched.

How do these hydrocarbons differ? -One of these hydrocarbons is branched. -One of these hydrocarbons has a double bond. -One of these hydrocarbons is longer than the other. -These hydrocarbons are identical. -One of these hydrocarbons has a ring structure.

One of these hydrocarbons is longer than the other. The hydrocarbon on the right is longer than the hydrocarbon on the left.

L-dopa is used to treat

Parkinson's disease

L-dopa is used to treat _____.

Parkinson's disease People with Parkinson's disease lack dopamine.

Which molecules show an appropriate number of bonds around each carbon atom?

Since carbon atoms are tetravalent (able to form four bonds), atoms may branch off a carbon atom in as many as four places. The ability of a carbon atom to form four different bonds allows carbon to form many different sizes and types of molecules. Carbon atoms may form chains, rings, or combinations of chains and rings. The tetravalence of carbon makes it particularly well-suited to forming the backbone of a huge diversity of organic molecules.

Classifying molecules by their functional groups

Some biologically important functional groups include the hydroxyl group, the carbonyl group, the carboxyl group, the amino group, the sulfhydryl group, and the phosphate group. Phosphate groups, for example, are an important part of the structure of ATP (adenosine triphosphate), an energy storage molecule in cells.

Testosterone and estradiol are male and female sex hormones, respectively, in many vertebrates. In what way(s) do these molecules differ from each other?

Testosterone and estradiol have different functional groups attached to the same carbon skeleton.

Which of the functional groups shown above is most likely to gain a proton and become positively charged? The amino group is most likely to gain a proton. The hydroxyl group is most likely to gain a proton. The carboxyl group is most likely to gain a proton

The amino group is most likely to gain a proton. An amino group acts as a base and can pick up protons from the surrounding medium, becoming positively charged.

Which of the following statements best describes the carbon atoms present in a seed-eating bird?

The carbon atoms ultimately came from carbon dioxide incorporated into sugars through photosynthesis.

Why are hydrocarbons insoluble in water?

The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.

Which of the following best describes cis-trans isomers?

They differ in their spatial arrangement around inflexible double bonds. Cis-trans isomers maintain the same covalent partnerships, but the atoms may be arranged differently.

Which of the following statements correctly describes cis-trans isomers?

They have variations in arrangement around a double bond.

Which of the following statements best describes the carbon atoms present in a seed-eating bird?

They were incorporated into organic molecules by plants, they were processed into sugars through photosynthesis, and they are ultimately derived from carbon dioxide.

A chemist wishes to make an organic molecule less acidic. Which of the following functional groups should be added to the molecule in order to do so?

amino

MAKE CONNECTIONS Which chemical group is most likely to be responsible for an organic molecule behaving as a base (see Concept 3.3, p. 53 in your textbook)?

amino

Stanley Miller's 1953 experiments assumed that early Earth's atmosphere contained

ammonia, methane, hydrogen gas, and water vapor.

Enantiomers are molecules that

are mirror images

Enantiomers are molecules that _____.

are mirror images

Research indicates that ibuprofen, a drug used to relieve inflammation and pain, is a mixture of two enantiomers; that is, molecules

are mirror images of one another.

Thalidomide and L-dopa, shown below, are examples of pharmaceutical drugs that occur as enantiomers, or molecules that

are mirror images of one another.

Compared to a hydrocarbon chain where all the carbon atoms are linked by single bonds, a hydrocarbon chain with the same number of carbon atoms, but with one or more double bonds, will

be more constrained in structure.

When Stanley Miller applied heat and electrical sparks to a mixture of simple inorganic compounds such as methane, hydrogen gas, ammonia, and water vapor, what compounds were produced?

both simple organic compounds and more complex organic compounds such as amino acids and hydrocarbons

Organic molecules with only hydrogens and five carbon atoms can have different structures in all of the following ways except

by forming enantiomers

The large diversity of shapes of biological molecules is possible because of the extensive presence of _____ in the molecules.

carbon With four electrons to share, carbon-based molecules can be multibranching and three-dimensionally variable.

The element present in all organic molecules is

carbon.

Amino acids are acids because they always possess which functional group?

carboxyl

Which chemical group can act as an acid?

carboxyl

Citric acid makes lemons taste sour. Which of the following is a functional group that would cause a molecule such as citric acid to be acidic?

carboxyl The carboxyl group can release a hydrogen ion when in solution.

Which two functional groups are always found in amino acids?

carboxyl and amino

A carbon atom is most likely to form what kind of bond(s) with other atoms?

covalent

Geometric isomers are molecules that

differ in the arrangement of their atoms about a double bond

Geometric isomers are molecules that _____.

differ in the arrangement of their atoms about a double bond

Differences among organisms are caused by

differences in the types and relative amounts of organic molecules synthesized by each organism.

These molecules are _____.

enantiomers These molecules are mirror images.

These molecules are _____.

geometric isomers These molecules differ in how their atoms are arranged about a double bond.

Most organic compounds contain carbon and

hydrogen In fact, some argue that carbon dioxide should not be considered an organic molecule because it does not contain hydrogen.

Molecules that have the same chemical formula (same numbers of each atom) but different three-dimensional shapes are called

isomers Isomers of carbon compounds can arise in several different ways.

The experimental approach taken in current biological investigations presumes that The experimental approach taken in current biological investigations presumes that The experimental approach taken in current biological investigations presumes that

living organisms can be understood in terms of the same physical and chemical laws that can be used to explain all natural phenomena.

This pair of molecules are _____.

not isomers These molecules have different molecular formulas.

Stanley Miller's 1953 experiments supported the hypothesis that

organic molecules can be synthesized abiotically under conditions that may have existed on early Earth.

The experiments of Wöhler, Kolbe, Miller, and other chemists invalidated the concept of vitalism by demonstrating that

organic molecules could be produced apart from living organisms using inorganic materials The vitalists proposed that a vital force restricted to living things was necessary to produce organic molecules.

What functional group is commonly used in cells to transfer energy from one organic molecule to another?

phosphate The addition and release of phosphate groups to and from ADP and ATP is how cells store chemical energy and expend it to accomplish work.

Vitalism gave way to mechanism, the view that

physical and chemical laws govern living systems Living things are subject to physical and chemical laws. They do not exist outside of them.

These molecules are _____.

structural isomers The two molecules differ in the covalent bond relationships among their atoms.

The complexity and variety of organic molecules is due to

the chemical versatility of carbon atoms.

What determines whether a carbon atom's covalent bonds to other atoms are in a tetrahedral configuration or a planar configuration?

the presence or absence of double bonds between the carbon atom and other

Variations in the reactive properties of different organic molecules are most closely associated with

the presence or absence of functional groups Functional groups are the most common participants in chemical reactions.

Which action could produce a carbonyl group?

the replacement of the -OH of a carboxyl group with hydrogen

Organic chemistry is currently defined as

the study of carbon compounds.

A carbon skeleton is covalently bonded to both an amino group and a carboxyl group. When placed in water it

would function as both an acid and a base