Chemistry 12
IUPAC Names of Alkanes
Alkanes with five or more carbon atoms in a chain are named using Greek prefixes: pent (5), hex (6), hept (7), oct (8), non (9), and dec (10).
Organic compounds
Always contains carbon and hydrogen atoms. May also contain other nonmetals such as oxygen, sulfur, nitrogen, phosphorus, or a halogen. is often found in common products such as gasoline, medicines, shampoos, plastics, and perfumes. We organize organic compounds by their functional groups, which are groups of atoms bonded in a specific way. Compounds that contain the same functional group have similar physical and chemical properties.
Conformations of Alkanes
Carbon atoms in a chain, connected by single C — C bonds can rotate so that groups attached to each carbon move freely about the C — C bond. can have different arrangements known as conformations. As the — CH3 groups rotate about the single C — C bond, they appear at different angles
Naming cycloalkenes
Cycloalkenes have a double bond within a ring structure and are named by assigning the double bond to be between carbon 1 and carbon 2 when a substituent is on the ring. do not need to include the numbers for the double bond. The carbon atoms in the ring are numbered to give the double bond numbers 1 and 2 and the lowest possible number to any substituents present.
Ethene (C2H4)
Ethene (C2H4), more commonly called ethylene, is an important plant hormone involved in promoting the ripening of fruits such as bananas. accelerates the breakdown of cellulose in plants, which causes flowers to wilt and leaves to fall from trees
Alkenes and Alkynes
Ethyne, commonly called acetylene, is used in welding, in which it reacts with oxygen to produce flames with temperatures above 3300 °C.
Markovnikov's Rule
When H2O adds to a double bond in an asymmetrical alkene, two products are possible. Markovnikov's rule states the following: The H — from H — OH attaches to the carbon that has the greater number of H atoms, and the — OH adds to the more substituted carbon atom.
Alkanes with Substituents
When an alkane has four or more carbon atoms, the atoms can be arranged so that a side group called a branch or substituent is attached to a carbon chain
Some common examples of aromatic compounds that we use for flavor are
anisole from anise, estragole from tarragon, and thymol from thyme.
Cycloalkanes
are cyclic alkanes. have two fewer hydrogen atoms than the open chain form. are named by using the prefix cyclo before the name of the alkane chain with the same number of carbon atoms
Melting and Boiling points- Cycloalkanes
have higher boiling points than the straight-chain alkanes with the same number of carbon atoms. have limited rotation of carbon bonds; they maintain their rigid structure and can be stacked closely together, which gives them many points of contact and attractions to each other.
The flat, symmetrical structure of benzene allows for
interactions between the cyclic structures, which contributes to the higher melting points and boiling points of benzene and its derivatives.
Addition of Alkenes: Polymerization
A polymer is a large molecule that consists of small, repeating units called monomers. Many of these polymers are produced by addition reactions of alkenes. In the past hundred years, the plastics industry has made synthetic polymers such as those used in carpeting, plastic wrap, nonstick pans, plastic cups, and rain gear. In medicine, synthetic polymers are used to replace diseased or damaged body parts such as hip joints, pacemakers, teeth, heart valves, and blood vessels.
Polymerization: Polyethylene
A polymer may contain as many as 1000 monomers. Polyethylene, a polymer made from ethylene monomers, is used in plastic bottles, film, and plastic dinnerware. Low-density polyethylene (LDPE) is flexible, breakable, less dense, and more branched than high-density polyethylene (HDPE). High-density polyethylene is stronger and more dense than LDPE, and it melts at a higher temperature than LDPE.
Line- Angle Structural Formulas
A simplified structure of organic molecules is called the line-angle structural formula. shows a zigzag line in which carbon atoms are represented as the ends of each line and as corners. Carbon atoms at the end are bonded to three hydrogen atoms. in the middle are bonded to two hydrogen atoms
Solubility and Density of Alkanes
Alkanes are nonpolar. insoluble in water. less dense than water. flammable in air. found in crude oil. If there is an oil spill in the ocean, the alkanes in the crude oil do not mix with the water but float on top, forming a thin layer on the surface.
Properties of Aromatic compounds
Aromatic compounds are less dense than water, although they are usually more dense than other hydrocarbons. Halogenated benzene compounds are denser than water. Aromatic hydrocarbons are insoluble in water and are used as solvents for other organic compounds. Only aromatic compounds containing strongly polar functional groups such as — OH or — COOH will be somewhat soluble in water. Benzene and other aromatic compounds are resistant to reactions that break up the aromatic system, although they are flammable.
Structural Formulas: C4H10
As butane (C4H10) rotates, sometimes the — CH3 groups line up in front of each other, and at other times they are opposite each other. Butane can be drawn using a variety of two-dimensional condensed structural formulas:
Naming Haloalkanes
Haloalkanes are alkanes with a halogen atom that replaces a hydrogen atom. are named by putting the substituents in alphabetical order. have the halo group numbered according to the carbon where it is attached to the alkane
Cis- Trans Isomers of Butene
In a cis isomer, the alkyl groups are attached on the same side of the double bond and H atoms are on the other side. In the trans isomer, the groups and H atoms are attached on opposite sides of the double bond
Condensed Structural Formulas
In a condensed structural formula, each carbon atom and its attached hydrogen atoms are written as a group. a subscript indicates the number of hydrogen atoms bonded to each carbon atom.
Addition reactions
In alkenes and alkynes, the double and triple bonds are very reactive and undergo hydrogenation, addition of H — H, and hydration, addition of H — OH to the carbons in the double or triple bond. undergo polymerization at high temperatures and pressure. are easily broken, providing electrons to form new bonds
Cis- Trans Isomers
In an alkene, the double bond is rigid and does not rotate. holds attached groups in fixed positions. makes cis-trans isomers (geometric isomers) possible when two different groups are attached to the carbon atoms on each side of the double bond. requires a prefix of cis or trans to reflect the arrangement of groups across the double bond.
Carbon compounds: Ethane (C2H6)
In ethane (C2H6), each tetrahedral carbon forms three covalent bonds to hydrogen and one to the other carbon. Three-dimensional and two-dimensional representations of ethane: (a) space-filling model,(b) ball-and-stick model, (c) wedge-dash model, (d) expanded structural formula, and (e) condensed structural formula.
Hydrogenation
In hydrogenation, hydrogen atoms add to the carbon atoms of a double bond or triple bond. a catalyst such as Pt, Ni, or Pd is used to speed up the reaction
Organic and inorganic compounds
Many inorganic compounds have high melting and boiling points. Inorganic compounds that are ionic are usually soluble in water, and most do not burn in air. Propane, C3H8, is an organic compound used as a fuel. NaCl, salt, is an inorganic compound composed of Na+ and Cl− ions.
Polymerization
Many of the synthetic polymers are made by addition reactions of small alkene monomers. Often, many polymerization reactions require high temperature. a catalyst. high pressure (over 1000 atm). In an addition reaction, a polymer grows longer as each monomer is added at the end of the chain.
Combustion of Alkanes- Methane, Propane
Methane is the natural gas we use to cook our food and heat our homes. The equation for the combustion of methane (CH4) is written as follows: CH4(g) + 2O2(g) CO2(g) + 2H2O(g) + energy Propane is the gas used in portable heaters and gas barbecues. The equation for the combustion of propane (C3H8) is written as follows: C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g) + energy
Organic chemistry is the study of carbon compounds.
Organic compounds such as vegetable oil contain carbon and hydrogen and are not soluble in water.
Properties of organic compounds
Organic compounds typically Have covalent bonds. have low melting and boiling points. are flammable and undergo combustion. are not soluble in water. Vegetable oil is a mixture of organic compounds and is not soluble in water.
Carbon compounds: Methane (CH4)
Structures are most often represented using their corresponding two-dimensional formulas. The expanded structural formula shows all of the atoms and the bonds connected to each atom. A condensed structural formula shows the carbon atoms each grouped with the attached number of hydrogen atoms. In methane (CH4), carbon forms four covalent bonds to hydrogen. Methane is tetrahedral and has bond angles of 109°. A hydrocarbon is referred to as a saturated hydrocarbon when all the bonds in the molecule are single bonds.
Alkane substituents
Substituents are atoms or groups of atoms attached to the carbon chain and include alkyl and halo groups. Alkyl groups are groups of carbon atoms attached to carbon chains. named in the IUPAC system with an yl ending. Halo substituents are halogen atoms attached to the carbon chain. named in the IUPAC system as fluoro, chloro, bromo, or iodo.
Naming Alkanes, Alkenes, and Alkynes
The IUPAC names for alkenes and alkynes are similar to those of alkanes. use the alkane name with the same number of carbon atoms, replacing the ane ending with ene. Cyclic alkenes are named as cycloalkenes.
Combustion of Alkanes
The carbon-carbon single bonds in alkanes are difficult to break, which makes them the least reactive family of organic compounds. However, alkanes burn readily in oxygen to produce carbon dioxide, water, and energy.
Benzene
an aromatic compound. a ring of six C atoms, each bonded to one H atom. a flat ring structure drawn with three alternating double bonds. represented by two structures, because the electrons are shared equally among all the C atoms. represented by a line-angle structural formula using a circle in the center instead of the alternating double bonds.
Alkanes
are formed by a continuous chain of carbon atoms. are named using the IUPAC (International Union of Pure and Applied Chemistry) system. have names that end in ane. use Greek prefixes to name carbon chains with five or more carbon atoms.
(Organic compounds) Hydrocarbons
are organic compounds that contain only carbon and hydrogen. In organic molecules, every carbon has four bonds. In methane (CH4), the carbon atom forms an octet by sharing its four valence electrons with four hydrogen atoms. Three-dimensional and two-dimensional representations of methane: (a) space-filling model, (b) ball-and-stick model, (c) wedge-dash model, (d) expanded structural formula, and (e) condensed structural formula.
Cis- Trans Isomers have different physical and chemical properties and
cannot occur when two groups are the same on one of the carbons.
The alkane-like nature of these plastic synthetic polymers makes them unreactive. They
do not decompose easily. are not biodegradable. have become significant contributors to pollution, on land and in the oceans. Efforts are being made to make them more degradable
Melting and Boiling points- Branched Alkanes
have lower boiling points than the straight-chain isomers. tend to be more compact, reducing the points of contact between the molecules. do not have linear shapes and cannot line up close to each other.
Melting and Boiling points- Alkanes
have the lowest melting and boiling points of organic compounds. contain only the nonpolar bonds of C — C and C — H. exhibit only weak dispersion forces in the solid and liquid states. Longer-chain alkanes have more dispersion forces.
Structural Isomers
have the same molecular formula with a different arrangement of atoms. have the same number of atoms bonded in a different order. Butane (C4H10) has two structural isomers: a straight chain and a branched chain.
