2.3 Formal Charges
2 min read•may 7, 2024
reveal how electrons are distributed in molecules, affecting their properties and reactivity. By calculating these charges, we can predict polarity, stability, and behavior in chemical reactions.
Understanding formal charges helps us make sense of molecular structure and bonding. This knowledge is crucial for predicting how compounds will interact, react, and behave in various chemical environments.
Formal Charges and Molecular Properties
Formal charge calculation process
Top images from around the web for Formal charge calculation process
Formal Charges and Resonance · Chemistry View original
Is this image relevant?
Formal charge - Wikipedia View original
Is this image relevant?
Formal Charges and Resonance | Chemistry View original
Is this image relevant?
Formal Charges and Resonance · Chemistry View original
Is this image relevant?
Formal charge - Wikipedia View original
Is this image relevant?
1 of 3
Top images from around the web for Formal charge calculation process
Formal Charges and Resonance · Chemistry View original
Is this image relevant?
Formal charge - Wikipedia View original
Is this image relevant?
Formal Charges and Resonance | Chemistry View original
Is this image relevant?
Formal Charges and Resonance · Chemistry View original
Is this image relevant?
Formal charge - Wikipedia View original
Is this image relevant?
1 of 3
- is the difference between the number of in an isolated atom and the number of electrons assigned to that atom in a molecule
- Assigned electrons include and half of
- General formula: Formal\:charge = [# \:of\:valence\:electrons] - [# \:of\:non-bonding\:electrons] - \frac{1}{2}[#\:of\:bonding\:electrons]
- Example: Dimethyl sulfoxide (, )
- Sulfur: 6 valence electrons, 1 non-bonding pair, 4 bonding pairs (8 bonding electrons)
- Oxygen: 6 valence electrons, 2 non-bonding pairs, 1 bonding pair (2 bonding electrons)
- Carbon and hydrogen atoms have no formal charges as they follow the
- Sulfur: 6 valence electrons, 1 non-bonding pair, 4 bonding pairs (8 bonding electrons)
- are essential for visualizing formal charges and electron distribution
Formal charges and molecular properties
- Formal charges indicate uneven distribution of electrons within a molecule
- Positive atom has fewer electrons than in its neutral state ()
- Negative formal charge atom has more electrons than in its neutral state ()
- Uneven electron distribution leads to and
- Bonds between atoms with different formal charges are polar (C-O in aldehydes)
- Molecules with polar bonds and asymmetric geometry have a net (acetone)
- Formal charges can help predict the most stable
- Resonance structures with the least separation of formal charges are more stable
- Negative formal charges are more stable on more electronegative atoms (oxygen vs carbon)
Molecular structure and geometry
- influence the arrangement of atoms in a molecule
- describes the arrangement of electron domains around a central atom
- refers to the three-dimensional arrangement of atoms in a molecule
- of atomic orbitals affects the shape and bonding capabilities of molecules
Applications of formal charge concepts
- Atoms with positive formal charges are (electron-seeking)
- Prone to attack
- carbon in aldehydes and ketones acts as an electrophile
- Atoms with negative formal charges are nucleophilic (electron-donating)
- Can act as bases or nucleophiles in reactions
- () are strong bases and nucleophiles
- molecules with both positive and negative formal charges
- High solubility in polar solvents due to strong intermolecular interactions (hydrogen bonding)
- Amino acids at physiological pH exist as zwitterions
- molecules with adjacent positive and negative formal charges
- Reactive intermediates in reactions like the Wittig reaction for alkene synthesis
- () react with carbonyls to form alkenes
Key Terms to Review (29)
Alkoxide Ions: Alkoxide ions are negatively charged species formed when an alkoxide group (R-O-) is detached from a neutral alkoxide compound. These ions are important intermediates in many organic reactions, particularly in the context of understanding formal charges.
Bond Polarity: Bond polarity refers to the unequal sharing of electrons between two atoms in a covalent bond, resulting in an asymmetric distribution of electron density and the creation of a partial positive and partial negative charge. This concept is crucial in understanding formal charges, polar reaction mechanisms, and the effects of substituents on acidity.
Bonding Electrons: Bonding electrons are the electrons that participate in the formation of chemical bonds between atoms. These electrons are responsible for the stability and reactivity of molecules, as they determine the strength and nature of the interactions between atoms.
Carbanions: A carbanion is a negatively charged carbon atom with three bonds and a lone pair of electrons. These reactive intermediates play a crucial role in various organic chemistry reactions and concepts, including formal charges, reaction intermediates, alkyne acidity, and Grignard reagents.
Carbocations: Carbocations are positively charged carbon-centered species that serve as key intermediates in many organic reactions. They are formed when a carbon atom loses a bonded electron, resulting in a deficiency of electrons and a positive charge on the carbon.
Carbonyl: The carbonyl group is a functional group consisting of a carbon atom double-bonded to an oxygen atom. It is a key structural feature in many organic compounds, including aldehydes, ketones, carboxylic acids, and esters, and plays a crucial role in their chemical reactivity and properties.
Dimethyl Sulfoxide (DMSO): Dimethyl sulfoxide (DMSO) is a colorless, odorless, and polar organic compound with the chemical formula (CH3)2SO. It is a versatile solvent that is widely used in various applications, including the study of formal charges in organic chemistry.
DMSO is particularly relevant in the context of formal charges, as it is a molecule that exhibits unique charge distribution and can provide insights into the concept of formal charges.
Dipole Moment: Dipole moment is a measure of the separation of electric charge within a molecule or chemical bond. It represents the magnitude and direction of the unequal distribution of positive and negative charges, which can influence the behavior and properties of a molecule.
Dipole moment (𝜇): A dipole moment is a measure of the separation of positive and negative electrical charges within a molecule, indicating the polarity of a bond or molecule. It is quantitatively expressed in units of Debye (D) and results from differences in electronegativity between bonded atoms.
DMSO: DMSO, or dimethyl sulfoxide, is a highly polar organic solvent known for its ability to dissolve both polar and nonpolar compounds. Its unique properties make it a valuable reagent in various chemical reactions, particularly in nucleophilic substitution processes, where it enhances the solubility of reactants and facilitates the formation of intermediates.
Electron Domains: Electron domains are the regions of space around an atom where electrons are found. They are a fundamental concept in understanding the shape and geometry of molecules, particularly in the context of hybridization and formal charges.
Electron-Pair Geometry: Electron-pair geometry, also known as molecular geometry, is the three-dimensional arrangement of atoms and electron pairs around a central atom in a molecule. This concept is closely related to the topic of formal charges, as the electron-pair geometry influences the distribution of electrons and the resulting formal charges on atoms.
Electrophilic: Electrophilic refers to a species or reagent that is attracted to or seeks out electron-rich regions, typically in organic chemistry reactions. These species are often positively charged or have a partial positive charge, and they interact with and form bonds with nucleophiles, which are electron-rich species.
Formal charge: Formal charge is a mathematical charge assigned to an atom in a molecule, representing the difference between the number of valence electrons in an isolated atom and the number assigned to it in the molecule. It helps determine molecular structure by indicating electron distribution.
Formal Charge: Formal charge is a concept in chemistry that describes the hypothetical charge assigned to an atom in a molecule, based on the difference between the number of valence electrons of the isolated atom and the number of electrons assigned to that atom in the molecule. It provides a way to understand the distribution of electrons in a molecule and is an important tool in predicting the stability and reactivity of chemical species.
Formal charges: Formal charge is a concept used to identify the charge distribution within a molecule, calculated by assuming that electrons in chemical bonds are shared equally between atoms. It helps in determining the most stable structure of a molecule by comparing the number of valence electrons an atom has in a molecule with the number it would have in its neutral state.
Hybridization: Hybridization is a fundamental concept in chemistry that describes the process of mixing atomic orbitals to form new hybrid orbitals, which are used to explain the geometry and bonding patterns of molecules. This term is closely related to the development of chemical bonding theory, valence bond theory, and molecular orbital theory, as well as the structure and properties of various organic compounds.
Lewis structures: Lewis structures are visual representations of the valence electrons in molecules, showing how atoms are bonded together and the lone pairs of electrons that may exist. They serve as a foundational tool in organic chemistry for understanding molecular geometry, bonding, and reactivity.
Lewis Structures: Lewis structures are a graphical representation of the bonding in molecules and polyatomic ions, where shared or unshared electron pairs are shown as lines or dots, respectively. They are used to visualize the arrangement of atoms and the distribution of valence electrons in a chemical species.
Molecular Geometry: Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule, which significantly influences the molecule's physical and chemical properties. The shape of a molecule is determined by the arrangement of its constituent atoms and the presence of lone pairs of electrons, which can repel bonded atoms and alter the geometry. Understanding molecular geometry is crucial for predicting molecular behavior, reactivity, and interactions.
Molecular Polarity: Molecular polarity refers to the unequal distribution of electrons within a molecule, resulting in an asymmetric charge distribution and the creation of a dipole moment. This concept is essential in understanding the behavior and properties of molecules in various chemical contexts.
Non-bonding Electrons: Non-bonding electrons are electrons in an atom or molecule that are not involved in the formation of covalent bonds. They are also known as lone pair electrons and occupy space around the central atom without participating in chemical bonding.
Nucleophilic: A nucleophile is a species that donates an electron pair to form a new covalent bond. Nucleophilicity is a key concept in organic chemistry, as it governs the reactivity of many important chemical reactions, including those discussed in the topics of formal charges, Grignard reagents, and substituent effects on acidity.
Octet Rule: The octet rule is a fundamental principle in chemistry that states that atoms tend to form stable chemical bonds by achieving a full outer electron shell, typically containing eight electrons. This rule helps explain the formation of chemical bonds and the stability of various chemical compounds.
Phosphonium Ylides: Phosphonium ylides are a class of organic compounds containing a positively charged phosphorus atom bonded to a negatively charged carbon atom. They are important intermediates in organic synthesis, particularly in the Wittig reaction, which allows for the formation of carbon-carbon double bonds.
Resonance Structure: Resonance structure is a concept in organic chemistry that describes the delocalization of electrons within a molecule, resulting in the existence of multiple valid Lewis structures that contribute to the overall bonding and stability of the compound. This concept is particularly important in understanding the behavior and reactivity of conjugated systems and aromatic compounds.
Valence Electrons: Valence electrons are the outermost electrons in an atom that participate in chemical bonding. They are the electrons that determine the chemical properties and reactivity of an element.
Ylides: Ylides are a class of organic compounds containing a positively charged atom (usually phosphorus or sulfur) bonded to a negatively charged atom, typically carbon. They are important intermediates in various organic reactions, particularly in the Wittig reaction for the formation of alkenes.
Zwitterions: A zwitterion is a molecule that contains both a positive and a negative charge within the same structure, resulting in an overall neutral charge. These unique species play an important role in understanding formal charges and the behavior of organic compounds.