2356 Rape is the forcible violation of the sexual intimacy of another person. It does injury to justice and charity. Rape deeply wounds the respect, freedom, and physical and moral integrity to which every person has a right. It causes grave damage that can mark the victim for life. It is always an intrinsically evil act. Graver still is the rape of children committed by parents (incest) or those responsible for the education of the children entrusted to them.
2376 Techniques that entail the dissociation of husband and wife, by the intrusion of a person other than the couple (donation of sperm or ovum, surrogate uterus), are gravely immoral. …
2390 … The sexual act must take place exclusively within marriage. Outside of marriage it always constitutes a grave sin and excludes one from sacramental communion. …
2396 Among the sins gravely contrary to chastity are masturbation, fornication, pornography, and homosexual practices.
2400 Adultery, divorce, polygamy, and free union are grave offenses against the dignity of marriage.
2528 “Everyone who looks at a woman lustfully has already committed adultery with her in his heart” (Mt 5:28).
2529 The ninth commandment warns against lust or carnal concupiscence.