The structure for the DNA base cytosine is shown.

Which of the following is not a resonance structure of cytosine? (LO 7.13) (a)
(b)
(c)
(d)

Verified step by step guidance

1. Identify the structure of cytosine and compare it with the given structure of thymine.
2. Recall the rules for drawing resonance structures, which include the movement of electrons but not atoms.
3. Examine each resonance structure option (a, b, c, d) for cytosine and determine if they follow the resonance rules.
4. Check if any of the options involve breaking the resonance rules, such as moving atoms or violating the octet rule.
5. Identify the option that does not represent a valid resonance structure of cytosine.

Key Concepts

Resonance Structures

Resonance structures are different ways of drawing the same molecule that illustrate the delocalization of electrons. They are used to represent molecules where the actual structure is a hybrid of these forms, providing a more accurate depiction of electron distribution. In the case of cytosine, resonance structures help explain the stability and reactivity of the molecule.

Cytosine Structure

Cytosine is one of the four main bases found in DNA and RNA, characterized by its pyrimidine ring structure. It contains nitrogen and oxygen atoms, which play crucial roles in hydrogen bonding and base pairing. Understanding its structure is essential for recognizing how it interacts with other nucleobases and contributes to the genetic code.

Identifying Non-Resonance Structures

Identifying non-resonance structures involves recognizing which proposed structures do not accurately represent the electron distribution of the molecule. This requires knowledge of the rules governing resonance, such as the conservation of atom connectivity and the placement of electrons. Analyzing the given options critically helps in determining which structure deviates from the valid resonance forms.