Question

For each of the following, fill in the blank with the correct response. All of these fill-in-the-blank problems pertain to material covered in the sections on alkanes, alkenes and alkynes, aromatic hydrocarbons, and hydrocarbon derivatives. a. The first "organic" compound to be synthesized in the laboratory, rather than being isolated from nature, was which was prepared from b. An organic compound whose carbon-carbon bonds are all single bonds is said to be c. The general orientation of the four pairs of electrons around the carbon atoms in alkanes is d. Alkanes in which the carbon atoms form a single unbranched chain are said to be alkanes. e. Structural isomerism occurs when two molecules have the same number of each type of atom but exhibit different arrangements of the between those atoms. f. The systematic names of all saturated hydrocarbons have the ending added to a root name that indicates the number of carbon atoms in the molecule. g. For a branched hydrocarbon, the root name for the hydrocarbon comes from the number of carbon atoms in the continuous chain in the molecule. h. The positions of substituents along the hydrocarbon framework of a molecule are indicated by the of the carbon atom to which the substituents are attached. i. The major use of alkanes has been in reactions, as a source of heat and light. j. With very reactive agents, such as the halogen elements, alkanes undergo \(\longrightarrow\) reactions, whereby a new atom replaces one or more hydrogen atoms of the alkane. k. Alkenes and alkynes are characterized by their ability to undergo rapid, complete reactions, by which other atoms attach themselves to the carbon atoms of the double or triple bond. 1\. Unsaturated fats may be converted to saturated fats by the process ofm. Benzene is the parent member of the group of hydrocarbons called \(\quad\) hydrocarbons. n. An atom or group of atoms that imparts new and characteristic properties to an organic molecule is called \(a\) group. 0\. \(\mathrm{A}\) alcohol is one in which there is only one hydrocarbon group attached to the carbon atom holding the hydroxyl group. p. The simplest alcohol, methanol, is prepared industrially by the hydrogenation of q. Ethanol is commonly prepared by the of certain sugars by yeast. r. Both aldehydes and ketones contain the they differ in where this group occurs along the hydrocarbon chain. s. Aldehydes and ketones can be prepared by of the corresponding alcohol. t. Organic acids, which contain the group, are typically weak acids. u. The typically sweet-smelling compounds called result from the condensation reaction of an organic acid with an

Short answer

a. urea, ammonium chloride, and silver cyanate b. saturated c. tetrahedral d. straight-chain or normal alkanes e. bonds f. -ane g. the longest continuous chain h. number i. combustion j. substitution k. addition l. hydrogenation m. aromatic n. functional o. primary p. carbon monoxide q. fermentation r. carbonyl group s. oxidation t. carboxyl group u. esters

Step-by-step solution

a. Synthesized organic compound

The first "organic" compound to be synthesized in the laboratory, rather than being isolated from nature, was urea which was prepared from ammonium chloride and silver cyanate.

b. Carbon-carbon single bonds

An organic compound whose carbon-carbon bonds are all single bonds is said to be saturated.

c. Electron orientation in alkanes

The general orientation of the four pairs of electrons around the carbon atoms in alkanes is tetrahedral.

d. Single unbranched chain alkanes

Alkanes in which the carbon atoms form a single unbranched chain are said to be straight-chain or normal alkanes.

e. Structural isomerism

Structural isomerism occurs when two molecules have the same number of each type of atom but exhibit different arrangements of the bonds between those atoms.

f. Saturated hydrocarbons naming

The systematic names of all saturated hydrocarbons have the ending -ane added to a root name that indicates the number of carbon atoms in the molecule.

g. Branched hydrocarbon root name

For a branched hydrocarbon, the root name for the hydrocarbon comes from the number of carbon atoms in the longest continuous chain in the molecule.

h. Substituent positions on hydrocarbon

The positions of substituents along the hydrocarbon framework of a molecule are indicated by the number of the carbon atom to which the substituents are attached.

i. Alkane major use

The major use of alkanes has been in combustion reactions, as a source of heat and light.

j. Alkanes reaction with halogens

With very reactive agents, such as the halogen elements, alkanes undergo substitution reactions, whereby a new atom replaces one or more hydrogen atoms of the alkane.

k. Alkene and alkyne reactions

Alkenes and alkynes are characterized by their ability to undergo rapid, complete addition reactions, by which other atoms attach themselves to the carbon atoms of the double or triple bond.

l. Converting unsaturated fats

Unsaturated fats may be converted to saturated fats by the process of hydrogenation.

m. Benzene hydrocarbons

Benzene is the parent member of the group of hydrocarbons called aromatic hydrocarbons.

n. Characteristic properties in organic molecule

An atom or group of atoms that imparts new and characteristic properties to an organic molecule is called a functional group.

o. Alcohol definition

A primary alcohol is one in which there is only one hydrocarbon group attached to the carbon atom holding the hydroxyl group.

p. Methanol preparation

The simplest alcohol, methanol, is prepared industrially by the hydrogenation of carbon monoxide.

q. Ethanol preparation

Ethanol is commonly prepared by the fermentation of certain sugars by yeast.

r. Aldehydes and ketones

Both aldehydes and ketones contain the carbonyl group; they differ in where this group occurs along the hydrocarbon chain.

s. Aldehydes and ketones preparation

Aldehydes and ketones can be prepared by oxidation of the corresponding alcohol.

t. Organic acids

Organic acids, which contain the carboxyl group, are typically weak acids.

u. Sweet-smelling compounds

The typically sweet-smelling compounds called esters result from the condensation reaction of an organic acid with an alcohol.

Key concepts

Structural Isomerism

Structural isomerism refers to the phenomenon where compounds with the same molecular formula have different structural arrangements of atoms, leading to distinct properties. This arises because the atoms can be connected in multiple ways to create various structures. For example, butane (C₄H₁₀) has two structural isomers: n-butane with a straight chain and isobutane with a branched chain. Understanding isomerism is crucial in organic chemistry as it explains why different substances can have similar formulas but different chemical behaviors.

In educational resources, emphasizing the concept of isomerism is vital for students to recognize the diversity in organic compounds and predict how this diversity affects their physical and chemical properties.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They serve as the site of reactivity in an organic compound. Common examples include hydroxyl groups (-OH) in alcohols, carboxyl groups (-COOH) in organic acids, and carbonyl groups (>C=O) in ketones and aldehydes. Each type imparts distinct chemical properties to the molecules they are part of.

Teaching students about functional groups helps them understand and predict the reactivity and interactions of organic compounds. It's helpful to use visual aids or molecular models to illustrate how different functional groups modify the chemical behavior of molecules.

Alkane Combustion

Alkane combustion is a highly exothermic chemical reaction where alkanes react with oxygen to produce carbon dioxide, water, and heat. It is a type of oxidation-reduction reaction, commonly used in heaters and engines. The complete combustion of an alkane follows the general equation: C_xH_y + (x + y/4)O₂ → xCO₂ + (y/2)H₂O + heat.

When teaching this topic, it's integral to stress the importance of proper oxygen supply to ensure complete combustion, preventing the production of harmful carbon monoxide. Understanding combustion allows students to grasp energy transformations and the environmental impact of burning fossil fuels.

Hydrocarbon Substitution Reactions

In hydrocarbon substitution reactions, an atom or group of atoms in a hydrocarbon molecule is replaced by another atom or group. This is common with alkanes reacting with halogens under specific conditions (light or heat) to form haloalkanes. The reaction follows the general pattern: R-H + X₂ → R-X + HX, where R is the alkyl group, H is a hydrogen atom, X is a halogen.

Teaching this topic can revolve around the concept of 'free radicals' and the initiation, propagation, and termination steps in a radical chain reaction. It's essential for students to understand the mechanisms involved and the conditions needed for such reactions to occur.

Addition Reactions of Alkenes and Alkynes

Addition reactions occur when unsaturated hydrocarbons (alkenes and alkynes) react with other substances to become saturated, adding across the carbon-carbon multiple bonds. Alkenes have double bonds (C=C), and alkynes have triple bonds (C≡C), making them more reactive than alkanes.

For example, the addition of hydrogen (hydrogenation) turns alkenes and alkynes into alkanes. It's important for students to understand that catalysts, such as platinum or nickel, are often required to initiate these reactions. Emphasizing the concept of 'electrophilic addition' will help students understand how and why these reactions occur and their importance in industrial processes like the production of polymers.

Aromatic Hydrocarbons

Aromatic hydrocarbons, or arenes, are a class of hydrocarbons that include benzene as their structural motif. These compounds are characterized by a ring of carbon atoms with alternating double bonds, known as the aromatic ring. The stability and unique chemistry of aromatic rings come from 'resonance,' a concept that describes the delocalization of electrons across the ring.

When presenting this topic, highlighting the concept of resonance and its impact on the chemical stability of these compounds can deepen students' understanding. It's also important to discuss the wide range of aromatic compounds' applications, from pharmaceuticals to dyes, and their environmental concerns.

Hydrogenation Process

The hydrogenation process involves the addition of hydrogen (H₂) to unsaturated hydrocarbons to convert them into saturated hydrocarbons. Using a catalyst, usually a metal such as palladium, platinum, or nickel, the process typically converts liquid oils into solid fats, as seen in the food industry to produce margarine from vegetable oils.

In education, it's useful to teach this process in the context of both organic chemistry and its practical implications, like its role in changing the physical properties of substances and the implications on health when used to process food.

Carbonyl Group in Aldehydes and Ketones

The carbonyl group (>C=O) is a functional group present in both aldehydes and ketones, but its location differs within the molecule: at the end of the carbon chain in aldehydes and internally in ketones. The presence of the carbonyl group makes these compounds polar and influences their reactivity, especially in nucleophilic addition reactions.

Clarifying the electron geometry of the carbonyl carbon (trigonal planar) and its electrophilic character provides a solid foundation for students to understand reactions involving aldehydes and ketones. It's also beneficial to discuss the importance of these compounds in biochemistry and the pharmaceutical industry.

Carboxyl Group in Organic Acids

Organic acids, such as acetic acid and citric acid, are characterized by the presence of a carboxyl group (-COOH). This group is composed of a carbonyl and a hydroxyl group attached to the same carbon atom, making organic acids weak acids. They can donate a proton (H+) due to the polar nature of the O-H bond within the carboxyl group.

Teaching about the acidic nature of the carboxyl group, its impact on molecule solubility, and the formation of derivatives like esters and amides helps students understand the principles of acidity and the versatility of organic compounds.

Ester Condensation Reactions

Ester condensation reactions, also known as esterification, are chemical reactions where organic acids react with alcohols to form esters and water. This process typically requires an acid catalyst and is reversible. Esters are known for their pleasant fragrances and are used in making perfumes and flavorings.

For students, learning this reaction strengthens their grasp of equilibrium and reaction kinetics in organic chemistry. Also, discussing real-life examples of esters can make the topic more engaging and relatable.