Chapter 12 homework CHEM140
Alkanes react with oxygen _________ and with halogens __________.
(combustion) (halogenation)
What is the IUPAC name for the HFC that has the formula CH2FCF3? (Hint: you must use a number to indicate the location of each substituent F atom.)
1,1,1,2-tetrafluoroethane
What is the IUPAC name for the HCFC that has the formula CHCl2CF3?
1,1,1-trifluoro-2,2-dichloroethane
Give the common and IUPAC names for each compound. CH3CH2CH2Br
1-bromopropane The alkyl group (CH3CH2CH2-) is a propyl group, and the halogen is bromine (Br). The common name is therefore propyl bromide. For the IUPAC name, the prefix for bromine (bromo) is combined with the name for a three-carbon chain (propane), preceded by a number identifying the carbon atom to which the Br atom is attached, so the IUPAC name is 1-bromopropane.
How many hydrogen atoms are present in 3-methylpentane?
14 The formula for 3-methylpentane is C₆H₁₄.
How many covalent bonds does oxygen typically form in an organic compound?
2
Give the common and IUPAC names for each compound. (CH3)2CHCl
2-chloropropane The alkyl group [(CH3)2CH-] has three carbon atoms, with a chlorine (Cl) atom attached to the middle carbon atom. The alkyl group is therefore isopropyl, and the common name of the compound is isopropyl chloride. For the IUPAC name, the Cl atom (prefix chloro-) attached to the middle (second) carbon atom of a propane chain results in 2-chloropropane.
Name the following using correct IUPAC nomenclature: CH3CH2CH(CH3)CH3
2-methylbutane
Which compound corresponds to a saturated hydrocarbon? 3-methylpentane 2-butyne cyclooctene 3-hexene 2-propanol
3-methylpentane Hydrocarbons are compounds that only contain carbon and hydrogen and are classified on the types of carbon-carbon bonds. Saturated hydrocarbons have carbon atoms that share single bonds and are classified as alkanes. 3-methylpentane is an alkane containing only single carbon-carbon bonds and is a saturated hydrocarbon.
The number of covalent bonds carbon forms in organic compounds is ____.
4
How many carbon atoms are present in 2-methylbutane?
5 The base alkane butane has 4 carbon atoms. Adding a methyl group increases the number of carbons by 1 for a total of 5.
How many carbon atoms are present in hexane?
6
How many carbon atoms are present in 3-methylpentane?
6 The base alkane pentane has 5 carbon atoms. Adding a methyl group increases the number of carbons by 1 for a total of 6.
What does carbon tetrachloride (CCl4) form when it reacts with water at high temperatures?
A deadly phosgene (COCl2) gas, which makes the use of CCl4 in fire extinguishers particularly dangerous
Why do alkanes usually not react with ionic compounds such as most laboratory acids, bases, oxidizing agents, or reducing agents?
Alkanes are nonpolar; they do not attract ions.
What physical properties explain the observation that octane is insoluble in water? A) octane has a lower boiling point than water. B) octane is non-polar and water is polar. C) both compounds have covalent bonds. D) water has a low molecular weight.
B) octane is non-polar and water is polar. Octane is non-polar and water is highly polar therefore octane is not soluble in water.
Which of the following is NOT a constitutional isomer of the others? A) ethyl methyl ether B) propanone C) 1-propanol D) 2-propanol E) None of these are constitutional isomers of each other.
B) propanone propanone has the molecular formula C₃H₆O, while ethyl methyl ether, 1 propanol, and 2-propanol have molecular formulas of C₃H₈O.
Why is it rare for only carbon dioxide, water, and heat to be formed from a methane reation?
Because the conditions are rarely ideal
The general formula for an alkane is _____
C(n)H(2n+2) A straight, open chain, hydrocarbon will have two hydrogens on each carbon with an extra hydrogen on each end carbon, for a total of 2n+2 hydrogen atoms. Adding a branch in the chain will remove one hydrogen from the branch carbon, but create an additional terminal carbon with three hydrogens, still adding only two hydrogens per carbon. Therefore the general formula is C(n)H(2n+2).
Which of the following formulas represents an organic compound? KCl NH3 Cl2 C3H8 SiH4
C3H4 Organic compounds contain carbon (C). The only compound in the list containing carbon is C₃H₈.
Write the condensed structural formulas for the two isomers that have the molecular formula C3H7Br. Give the common name and the IUPAC name of each.
CH3CH2CH2Br, propyl bromide, 1-bromopropane; CH3CHBrCH3, isopropyl bromide, 2-bromopropane
What are some examples of halogenated hydrocarbons?
CH3CH2Cl CH3CHBrCH2Br CH3CHICH2Cl
Write the condensed structural formula for each compound. methyl chloride
CH3Cl
What reaction does methane (CH4) have when heat and oxygen are present?
CH4 + 2O2 --> Co2 + 2H2o + heat
Write the condensed structural formula for each compound. chloroform
CHCl3
What is a by-product of methane when the oxygen supply is limited?
Carbon Monoxide (CO) 2CH4 + 3O2 → 2CO + 4H2O
What is CH2Cl2 derived from CH4 (methane)?
Common name: IUPAC name: Some important uses:
What is CCl4 derived from CH4 (methane)?
Common name: carbon tetrachloride IUPAC name: tetrachloromethane Some important uses: dry-cleaning solvent and fire extinguishers (but no longer recommended for use)
What is CCl3F derived from CH4 (methane)?
Common name: chlorofluiricarbon-11 (CFC-11) IUPAC name: trichlorofluoromethane Some important uses: foaming plastics
What is CCl2F2 derived from CH4 (methane)?
Common name: chlorofluorocarbon-12 (CFC-12) IUPAC name: dichlorodifluoromethane Some important uses: refrigerant
What is CHCl3 derived from CH4 (methane)?
Common name: chloroform IUPAC name: dichloromethane Some important uses: laboratory and industrial solvent
What is CH3CH2Cl derived from CH3CH3?
Common name: ethyl chloride IUPAC name: chloroethane Some important Uses: local anesthetic
What is ClCH2CH2Cl derived from CH3CH3?
Common name: ethylene dichloride IUPAC name: 1,2-dichloroethane Some important uses: solvent for rubber
What is CBrF3 derived from CH4 (methane)?
Common name: halon-1301 IUPAC name: bromotrifluoromethane Some important uses: fire extinguisher systems
What is CH3CL derived from CH4 (methane)?
Common name: methyl chloride IUPAC Name: chloromethane Some important uses: refrigerant; the manufacture of silicones, methyl cellulose, and synthetic rubber
What is CCl3CH3 derived from CH3CH3?
Common name: methylchloroform IUPAC name: 1,1,1-trichloroethane Some important uses: solvent for cleaning computer chips and molds for shaping plastics
What are halogenated hydrocarbons?
Compounds in which one or more hydrogen atoms of a hydrocarbon have been replaced by halogen atoms
What is the formula for 2,3,4-trimethylheptane?
C₁₀H₂₂
Which of the following straight-chain alkanes has the highest boiling point?
C₁₀H₂₂ The boiling point of straight-chain alkanes increases with increasing molar mass. Thus, the heavier the straight-chain alkane is, the higher the boiling point.
Which molecular formula could not be a straight-chain alkane? A) C₃H₆ B) C₂H₆ C) C₅H₁₂ D) C₆H₁₄ E) C₄H₁₀
C₃H₆ A straight-chain alkane adopts the general formula CnH2n+2CnH2n+2 to account for having the maximum number of hydrogen atoms (2n+2) for the given number of carbon atoms (n). C3H6C3H6 adopts the formula CnH2nCnH2n and could not be a straight-chain alkane.
Which molecular formula corresponds to a saturated hydrocarbon? A) C₆H₁₂ B) C₅H₁₀ C) C₄H₈ D) C₇H₁₂ E) C₃H₈
C₃H₈ C₃H₈ adopts the general formula CnH2n+2CnH2n+2 which corresponds to a saturated hydrocarbon like a straight-chain alkane that has the maximum number of hydrogen atoms (2n+2) for the given number of carbon atoms (n).
Which of the following formulas represents a straight-chain alkane? A) C₂H₄ B) C₃H₈ C) C₂H₂ D) C₄H₆
C₃H₈ The formula for a straight-chain alkane is CnH2n+2CnH2n+2. C₃H₈ is propane and follows the general formula CnH2n+2CnH2n+2.
Which molecular formula corresponds to a saturated hydrocarbon? A) C₈H₁₆ B) C₉H₁₈ C) C₄H₁₀ D) C₇H₁₄ E) C₁₀H₂₀
C₄H₁₀ C₄H₁₀ adopts the general formula CnH2n+2CnH2n+2 which corresponds to a saturated hydrocarbon like a straight-chain alkane that has the maximum number of hydrogen atoms (2n+2) for the given number of carbon atoms (n).
What is the formula of 2-methylpropane?
C₄H₁₀ The base alkane is propane with 3 carbon atoms and a methyl substituent (-CH₃) present on carbon 2 to give a complete formula of C₄H₁₀.
What is the formula for the 2,2-dimethylpropane?
C₅H₁₂ The base alkane is propane with 3 carbon atoms. Two methyl substituents (-CH₃) are present on carbon-2 to give a complete formula of C₅H₁₂.
Which molecular formula corresponds to a straight-chain alkane? A) C₇H₁₂ B) C₆H₁₄ C) C₉H₁₈ D) C₅H₁₀ E) C₃H₆
C₆H₁₄ C₆H₁₄ adopts the general formula CnH2n+2CnH2n+2 which corresponds to a saturated hydrocarbon like a straight-chain alkane that has the maximum number of hydrogen atoms (2n+2) for the given number of carbon atoms (n)
What is the formula of 3-ethyl-2-methylhexane?
C₉H₂₀ The base alkane is hexane with 6 carbon atoms with ethyl substituent (-CH₂CH₃) on carbon-3 and a methyl substituent (-CH₃) present on carbon-2 to give a complete formula of C₉H₂₀
Which of the following is the correct IUPAC name for a structural (constitutional) isomer of pentane? I. 1-methylbutane II. 2,2-dimethylpropane III. 3-methylbutane A) I only B) I and II only C) I and III only D) II only E) I, II, and III
D) II only 1-Methylbutane should be called pentane and 3-methylbutane should be called 2-methylbutane, so 2,2-dimethylpropane is the only correct IUPAC name. Name I is identical to pentane, but a non-IUPAC name for it. Name III begins the carbon count from the wrong end, so is misnamed.
Organic compounds do not occur naturally. True False
False
What is the lightest halogen?
Fluorine (F2)
Alkyl halides with a larger number of carbon atoms are usually given
IUPAC names
Are positive or negative ions attracted to a nonpolar molecule?
No
Does anything happen when alkanes are mixed with oxygen at room temperature?
No
Reaction or no reaction CH3CH2CH2CH3 + H+ Butane + H+
No reaction
Reaction or no reaction CH3CH2CH2CH3 + MnO4 Butane + MnO4
No reaction
Reaction or no reaction CH3CH2CH2CH3 + OH- Butane + OH-
No reaction
How are alkyl halides named?
The IUPAC system uses the name of the parent alkane with a prefix indicating the halogen substituents, preceded by number indicating the substituent's location
What do alkanes react with in the presence of ultraviolet light or at high temperatures to yield chlorinated and brominated alkanes?
The halogens chlorine (Cl2) and bromine (Br2)
What are the two parts of the common names of alkyl halides?
The name of the alkyl group plus the stem f the name of the halogen, with the ending -ide
Isomers have _________.
The same molecular formula, but different structures "Isomer" comes from the Greek isomerēs 'sharing equally'. Isomers have the same molecular formula (i.e. the same number and kinds of atoms), but different structural arrangements of the atoms.
Why are alkanes sometimes called paraffins?
Why are alkanes sometimes called paraffins?
Is iodine (I2) relatively unreactive?
Yes
What is the simplest of the reactions of alkanes with halogens?
a single halogen atom substituted for a hydrogen atom of the alkane
What does the replacement of only one hydrogen atom in an alkane give?
an alkyl halide (or haloalkane)
What do the Cl atoms from the Chlorofluorocarbons broken down by ultraviolet radiation cause?
break down the ozone (O3) molecules that protect Earth from harmful UV radiation
Chlorofluorocarbons diffuse into the stratosphere, where they are
broken down by ultraviolet (UV) radiation to release Cl atoms
When are fluorinated and iodinated alkanes produced?
by indirect methods
What are the more closely related to alkanes, cycloalkanes compounds of?
carbon atoms are joined in a ring, or cyclic fashion.
If the reactants are adequately mixed and there is sufficient oxygen, what are the only products of Methane (CH4)?
carbon dioxide (CO2), water (H2O), and heat—heat for cooking foods, heating homes, and drying clothes
Many chlorinated hydrocarbons are suspected what?
carcinogens and are also known to cause severe liver damage
CH3CH2Cl has the common name ethyl chloride and the IUPAC name _______.
chloroethane
What is the most important reaction of alkanes?
combustion
What are the two important reactions that alkanes do go through?
combustion and halogenation
Alkyl halides with simple alkyl groups (one to four carbon atoms) are often called by
common names
What is a CFC? How are CFCs involved in the destruction of the ozone layer?
compounds containing Cl, F, and C; by releasing Cl atoms in the stratosphere
Alkanes substituted with both fluorine (F) and chlorine (Cl) atoms have been used as the
dispersing gases in aerosol cans, as foaming agents for plastics, and as refrigerants
Saturated hydrocarbons never contain ______ A) single bonds. B) single and double bonds. C) single and triple bonds. D) double and triple bonds. E) single, double, and triple bonds.
double and triple bonds. By definition saturated hydrocarbons contain only single bonds.
What are the prefixes for alkyl halides?
fluoro-, chloro-, bromo-, and iodo-
With what does the product of carbon monoxide commonly happen?
from unventilated or improperly adjusted gas heaters (Similar reactions with similar results occur with kerosene heaters.)
What do alkanes react with halogens to produce?
halogenated hydrocarbons
What does the reaction of alkanes with halogens produce?
halogenated hydrocarbons
The name of the alkane with the formula CH₃(CH₂)₄CH₃ is _____
hexane.
Alkane molecules are nonpolar and therefore generally do not react with
ionic compounds such as most laboratory acids, bases, oxidizing agents, or reducing agents
When ethyl chloride is sprayed on the skin, what happens?
it evaporates quickly, cooling the area enough to make it insensitive to pain. It can be used as an emergency general anesthetic
What happens when a flame or spark is in contact with alkanes?
it provides the activation energy, and a highly exothermic combustion reaction proceeds vigorously
Methanol will not dissolve in hexane because:
methanol is polar and hexane is nonpolar Methanol is polar as it contains an oxygen atom bound to a carbon atom and hexane is nonpolar as it is contains only carbon and hydrogen atoms. "Like dissolves like" therefore methanol will not dissolve in a nonpolar solvent like hexane.
When chorine reacts with excess methane (CH4), what does it give?
methyl chloride (CH3Cl) CH4 + Cl2 → CH3Cl + HCl With more chlorine, a mixture of products is obtained: CH3Cl, CH2Cl2, CHCl3, and CCl4.
The CFCs and other Cl- or bromine (Br)-containing ozone-destroying compounds are being replaced with
more benign substances like Hydrofluorocarbons (HFCs), such as CH2FCF3, which have no Cl or Br to form radicals, are one alternative.
What does Fluorine (F2) combine explosively with?
most hydrocarbons
Which halogen reacts most readily with alkanes? Which reacts least readily?
most readily: F2; least readily: I2
Alkanes are generally soluble in what type of solvents?
nonpolar Recall "like dissolves like". Alkanes are essentially nonpolar compounds and would therefore be soluble in nonpolar solvents.
hydrochlorofluorocarbons (HCFCs), such as CHCl2CF3. HCFC molecules break down more readily in the troposphere, and fewer
ozone-destroying molecules reach the stratosphere.
What are alkanes sometimes called because they undergo so few reactions?
paraffinis, from the Latin parum affinis, meaning "little affinity."
Bromine-containing compounds are widely used in fire extinguishers and as fire retardants on clothing and other materials. Because they too are toxic and have adverse effects on the environment, what are scientists doing?
scientists are engaged in designing safer substitutes for them, as for many other halogenated compounds.
Chlorofluorocarbons contribute to
the greenhouse effect in the lower atmosphere
