Lectures 9, 10, 11 - foundations of organic chemistry, e- config, bonding, molecular shape, HC families

why is carbon suited to organic chemistry

• Carbon forms four strong, stable bonds with elements including hydrogen, oxygen, nitrogen, and sulfur.


• It forms stable single, double, and triple bonds, enabling many molecular shapes and 3D structures.


• Its electronegativity supports a range of polar and nonpolar bonds.

hydrocarbons

contain only carbon and hydrogen. They may be acyclic (chains) or cyclic (rings), and may be straight-chain or branched.

functional groups

atoms or groups of atoms within a molecule that give it characteristic reactivity and influence properties such as boiling point and melting point.

saturated and unsaturated compounds

• Alkanes are saturated; their carbon atoms are connected by single bonds.

• Alkenes and alkynes are unsaturated because they contain carbon–carbon double or triple bonds.


• Fatty acid chains can be saturated or unsaturated.

octet rule

second-row elements cannot have more than eight valence electrons, whether as non-bonding electrons or in chemical bonds. atoms can have less than 8, but they cannot have more

Carbon ordinarily forms no more than four bonds. Nitrogen commonly forms three bonds and oxygen two, with remaining valence electrons in lone pairs.

noble gas configuration rule

describes the tendency of atoms to attain a filled valence shell; it helps explain typical bonding but is not itself a rule about the maximum number of bonds.

elements of the 2nd row usually want to fill up their octet (or if easier, lose all of their electrons in the 2nd energy level - called noble gas rule bc when octet is filled, the electrons configuration looks like a noble gas’ + its more a description of how many bonds an atom is likely to want to make, rather than how many it is allowed)

carbon’s ground state configuration

Carbon’s ground-state configuration is described as $1s^2\,2s^2\,2p^2$. Promotion and hybridization explain the four equivalent bonding orbitals used to form four bonds.

valency

the number of chemical bonds an atom can form

hybridisation

the mixing of atomic orbitals to produce an equivalent number of hybrid orbitals suited to bonding.


• sp³ carbon: Four equivalent orbitals; tetrahedral geometry; bond angles approximately 109.5°. Methane has four C–H sigma bonds.


• sp² carbon: Three coplanar hybrid orbitals; trigonal planar geometry; bond angles approximately 120°. One unhybridized p orbital remains perpendicular to the plane.


• sp carbon: Associated with linear geometry and a bond angle of 180°, as in an alkyne.

sigma and pi bonds

• A sigma bond forms through end-on overlap and contains a shared pair of electrons.


• A carbon–carbon double bond consists of one sigma bond and one pi bond. The pi bond is formed by overlap of unhybridized p orbitals.


• Pi-bond electrons are relatively accessible, making alkenes electron-rich and reactive.


• The notes give C–C sigma-bond length as 1.54 Å and C=C bond length as 1.34 Å; the double bond is shorter because the carbons are closer together

6 hydrocarbon families

• Alkanes are saturated hydrocarbons with the acyclic general formula CnH2n+2. Methane is CH₄; successive straight-chain examples include ethane, propane, butane, pentane, hexane, heptane, octane, nonane, and decane.


• Cycloalkanes have the general formula CnH2n for a single ring; examples include cyclopentane and cyclohexane.


• Alkenes contain a carbon–carbon double bond; the simplest is ethene, C₂H₄. Acyclic monoalkenes follow CnH2n

• Alkynes contain a carbon–carbon triple bond; the simplest is ethyne. Acyclic monoalkynes follow CnH2n-2

• Aromatic hydrocarbons include benzene and related compounds. Aromatic hydrocarbons may have common names, such as toluene (methylbenzene), phenol (hydroxybenzene), and aniline (aminobenzene).

• Aliphatic hydrocarbons do not contain aromatic components.

alkanes

Use the suffix -ane; identify and locate substituents. Example: 4-ethyl-3-methyloctane.

alkenes and alkynes

Indicate the position of the multiple bond in the parent name. Examples include but-2-yne, but-2-ynoic acid, and 4-methyloct-2-ene.

halogen substituents

Use fluoro-, chloro-, bromo-, and iodo-. Example: 3-bromo-3-methylheptane.

alcohols

Use -ol; when an alcohol is a substituent, use hydroxy-. Example: 3,5-dimethyloctan-4-ol.

aldehydes

Use -al; the aldehyde carbon is part of the parent chain. Example: heptanal.

ketones

Use -one and locate the carbonyl where needed. Example: 4-ethylheptan-2-one.

carboxylic acids

Use -oic acid. Example: heptanoic acid.

esters

Name the alkyl group attached to the ester oxygen, followed by the acid-derived name ending in -oate; the notes’ example is propyl hexanoate.

amines

Use -amine; identify substituents attached to nitrogen with an N-locant where needed. Example: N-methylpropylamine.

ethers

The notes introduce common naming as the substituent names followed by “ether,” for example ethyl methyl ether.

acid derivatives

• -yl chloride for acid chlorides

• -anhydride for anhydrides, -amide for amides

• -nitrile for nitriles.

aromatic substituents

• Names such as chlorobenzene, nitrobenzene, and methylbenzene are used. For disubstituted benzene, numerical locants may be replaced by ortho (1,2), meta (1,3), or para (1,4).


• Some aromatic compounds have familiar common names, including toluene, phenol, and aniline. Unusual names noted in the material include “Penguinone” for 3,4,4,5-tetramethylcyclohexa-2,5-dienone, as well as traumatic acid, moronic acid, psicose, and fucitol.

family groups w/ suffixes and prefixes

• aldehydes: -al / formyl

• ketones: -one / oxo-

• alcohol: -ol / hydroxy-

• amine: -amine / amino-

• ester:

• carboxylic acid:

• ether:

numerical prefixes (substituent)

• di

• tri

• tetra

• penta

• hexa

• hepta

• octa

• nona

• deca

priority lists in terms of order

1. carboxylic acids

2. aldehydes

3. ketones

4. alcohols

5. amines

6. alkenes

7. alkynes

8. alkanes

Carry A Keg Absolutely Abundant of Aliphatics