Ch 10 Organic Chemistry The chemistry of carbon

Ch. 10: Organic Chemistry � The chemistry of carbon compounds. � Mainly carbon and hydrogen atoms. � Many organic compounds occur naturally. � Thousands more can be synthesized by man.

Butane versus Na. Cl Inorganic Organic � Na. Cl, � C 4 H 10, 58. 5 g/mol � Bonding is ionic � M. P. = 801 o. C � B. P. = 1413 o. C � Dissolves in water � Will not burn 58. 1 g/mol � Bonding is covalent � M. P. = -138 o. C � B. P. = 0 o. C � Not soluble in water � Will burn in air

Learning Check � 1. 2. 3. 4. 5. Decide whether the property is that of pentane (C 5 H 12) or sodium sulfide (Na 2 S). Liquid at room temperature. Dissolves in water. Floats on the surface of water. Has a melting point of 1176 o. C. Burns in air easily.

Bonding � The bonding in all organic molecules is covalent. • Carbon has 4 valence electrons and hydrogen has 1. • • C • • H • • Carbon achieves an octet by forming four bonds.

Molecular Geometry � When carbon is bonded to four other atoms, it has a tetrahedral geometry.

Classes of Organic Compounds Aliphatic Saturated Alkanes Aromatic Unsaturated Cycloalkanes Benzene Ring Alkenes Alkynes

Methods for Writing Formulas � Molecular formula – shows the number of C and H atoms. � Ex) Propane, C 3 H 8. � Complete structural drawing – shows every single bond. H H H H–C–C–C–H H H H

Methods for Writing Formulas � Condensed structural formula – writes each C atom along with the number of H’s bonded to that carbon atom. � CH 3 – CH 2 – CH 3 � This is the preferred method for showing structures in this course.

IUPAC Nomenclature �A set of rules for naming all organic compounds. � Will not need to memorize the base names. � Names for one through ten carbons.

Alkane Base Names

Branched Alkanes � Butane, C 4 H 10, has more than one possible way to put four carbons together. � These two forms are called structural isomers. � Both can NOT be called butane!

IUPAC Nomenclature �A substituent is any group that is attached to the longest chain of carbon atoms. � CH 4 = methane, -CH 3 = methyl � CH 3 = ethane, -CH 2 CH 3 = ethyl � Cl = chloro, Br = bromo, I = iodo

IUPAC Nomenclature 1. 2. Determine the longest continuous chain of carbon atoms. Because the alkanes have free rotation, the chain may bend and twist in many shapes! Determine the type of substituents located on the longest chain. These are named in alphabetical order.

IUPAC Nomenclature 3. 4. 5. Number the longest chain such that the substituents have the lowest numbers. Name the substituents first followed by the base name. If two or more of the same substituent, then use prefixes. Every substituent MUST have a number in front of it indicating the position on the chain.

Cycloalkanes �A ring structure can be constructed from alkanes of three or more carbons by removing two hydrogen atoms. � Because they form a geometric shape, a shorthand method for their structure is that shape.

IUPAC Nomenclature � For ring structures, a mono-substituted ring does not need a number. � Why? ? ? � For di-substituted ring structures, number starting from the location of one the substituents and then go CW or CCW to give the next one the lowest number.

Haloalkanes �A haloalkane is placing a halogen (group 7 A) atom in place of a hydrogen atom. � Naming uses the fluoro, chloro, bromo, and iodo names. � Haloalkanes are used as refrigerants (CF 3 CH 2 F) and anesthetic agents (CF 3 CHCl. Br).

Names to Formulas � 1. 2. 3. 4. When converting a name to a condensed formula, you may want to do it in several steps. Base name = carbon backbone. Fill in substituent groups. Add H’s until each carbon has four bonds. Condense.

Properties of Alkanes � Alkanes are non-polar and, thus, do NOT dissolve in water. � Alkanes typically have a density of 0. 65 – 0. 70 g/m. L and will float on the surface of water. � All alkanes can be burned to produce energy. � Alkane + O 2 CO 2 + H 2 O

Crude Oil � Crude oil contains a variety of alkanes that are separated at an oil refinery. � The mixture is heated and then separated by fractions – that is, their differences in boiling points. � The lightest alkanes have the lowest boiling points and go to the top of the column.

Crude Oil

Crude Oil

Functional Groups � Alkanes are fairly unreactive and have little use to organic chemists. � Addition of other atoms like O, N, and S change the reactivity and properties of the boring alkanes and these are called functional groups. � Functional groups are classified into several common identifiers.

Functional Groups � Use of the letter “R” in generic formulas. � Alcohol � R-OH � Ex) – contain the hydroxyl (O-H) group. CH 3 CH 2 OH, CH 3 CHCH 3 OH

Functional Groups � Ether – an oxygen atom separating two alkyl groups. � R – O – R’ � Ex) CH 3 CH 2 -O-CH 2 CH 3 � Carbonyl group, C=O, is found in a couple of different ways.

Functional Groups � Aldehyde – the carbonyl group is on the end of the chain. � RCHO � Ex) CH 3 CH 2 C=O H

Functional Groups � Ketone – the carbonyl group is in the middle of the chain. � R(C=O)R’ � Ex) CH 3 – CH 3 O

Functional Groups � Carboxylic acid – has both the carbonyl and the hydroxyl groups. � RCOOH � Ex) CH 3 – C – OH O

Functional Groups � Ester – combines the carbonyl group and the ether group. � R-COO-R’ � Ex) CH 3 CH 2 – C – O – CH 3 O

Functional Groups � Amine – is a nitrogen atom that can be bonded to one, two, or three alkyl groups. � RNH 2 , R 2 NH, and R 3 N (note: R groups can be different!). � Ex) CH 3 – NH 2 , (CH 3)3 N

Functional Groups � Thiol – is a sulfur atom with one H atom (usually). � R-SH � CH 3 CH 2 – SH

Functional Groups � Alkenes, alkynes, and aromatics can also be considered as a functional group. � All of these will be discussed in greater details in the following chapters including naming, properties, and important reactions.